CHAPTER 7 - WWII JAPANESE MILITARY TACTICS - SECTION 3



TABLE OF CONTENTS









PART II - JUNGLE WARFARE.


SECTION I - GENERAL.

Before 1941, the Japanese had fought in areas where roads, railroads, and signal communications were not well developed, and where the mobility and self-sufficiency of the individual soldier were important elements. However, prior to the campaigns of Malaya, Burma, Netherlands East Indies, and Melanesia, it was necessary to place increased emphasis on the solution of problems of the logistics, equipment, and tactics of jungle warfare. Training, testing, and experimentation were conducted on Hainan Island and Formosa, where climate and terrain were similar to those of the areas of planned operations. The tactical doctrine evolved was designed to facilitate speed of movement and aggressive action in a type of warfare in which weaknesses in armor, artillery, and supply would not be the decisive factors that they would be in open warfare.




SECTION II - ADAPTATION OF TACTICAL PRINCIPLES TO JUNGLE WARFARE.


1. GENERAL.

In order to effect the three fundamental principles of surprise, mobility, and offensive action, the Japanese modified tactical practices to conform to the distinct jungle characteristics of limited visibity and difficulty of movement.





2. MOBILITY.

Facility of movement in the jungle is the basic problem, upon the solution of which depend surprise tactics and offensive action. In developing their jungle tactics, the Japanese assumed as a basic principle that movement could be made through even the densest jungle. Movement by water is easier than by land and, where practicable, the Japanese utilized native river craft in the areas of operation.



Figure 8. Typical Japanese jungle maneuver. 		Land movement off roads is facilitated by the ability of the Japanese soldier to carry loads, the lightness of his equipment, and the reduction of supply trains to the minimum. Operation plans envision the employment of captured supplies and equipment. Terrain features, especially high ground in swampy areas, are utilized as lines of advance, and advancing troops are preceded by units of pathcutters and engineers. By such methods, troops of battalion strength can cover about 5/8 of a mile in 2 hours, and 4 to 6 miles a day. Special care is used in crossing clearings; advance by bounds is made to avoid enemy artillery and mortar concentrations.


Full use is made of trails and roads. The advance and approach march usually differs from that in open terrain; in dense jungle it is not feasible to break' down into small columns and extend in width because separate tracks would have to be cut for each column. The usual formation is an advance in one column, with elements in the rearward echelons avail able for maneuver to either flank. Rapidity in the advance is limited only by the rate of march of the heavy-weapons elements. The formations of moving columns are designed to enable quick deployment into line to develop enemy resistance preparatory to envelopment or penetration. An advance guard precedes the main body during the march. When contact is made with hostile forces, the advance guard attempts to overcome enemy resistance. If the enemy's strength is too great, the advance guard deploys and tries to locate hostile automatic weapons. The main force deploys and, by envelopment, attempts to strike the enemy's rear. If the line of communicaL ions of the hostile force can be cut at weak points, the Japanese frequently establish road blocks designed to force the enemy to attempt a breakthrough in terrain chosen by the Japanese.




3. SURPRISE.

The dense vegetation of tl1e jungle offers ample opportunity for cover and concealment. The Japanese have exploited this natural protection to the utmost, with the result that large bodies of troops have been able to concentrate without detection. When an attack is launched, the Japanese often dispense with preparatory artillery fire and attempt to a pproach, unseen, within assaulting distance of the objective. At the time of attack, artillery fire is delivered in the area of the secondary or holding attack, while the main body moves silently to the flanks in order to launch the main effort.

Ruses and stratagems of all varieties are used to increase the element of surprise. The Japanese will attack over terrain formerly considered to be impassable; they will attack during bad weather conditions; and attempt infiltration to the rear of the defending troops in order to produce confusion and disorganization. Among the ruses employed are the use of firecrackers to simUlate machine-gun fire in sectors, where the Japanese have no intention to attack And shouting contradictory orders in the language of the defender, even to the extent of quoting the name and rank of officers actually present with the defending troops.



4. OFFENSIVE ACTION.

Since the Japanese did not contemplate the necessity for defensive action in the early stages of the war and app3.rently hope to fight the entire war without r esort to it, and since their national consciousness does not admit of any but the offensi ve solution to military problems, their tactical doctrine on jungle warfare is predominantly offensive.



SECTION III - RECONNAISSANCE.



The importance of reconnaissance as a necessity in successful operation in the jungle is recognized by the Japanese. When time prrmits, especially prior to a large scale operation, reconnaissance is detailed and thorough. Fifth columnists and personnel of the Military Intelligence Service are sent into the area, and the entire power of the intelligence system is centered on it. Yet, when a Japanese officer has to choose between detailed reconnaissance and the opportunity to strike an unexpected blow, reconnaissance usually is slighted or neglected altogether. The reconnaissance work generally is good, though there is more emphasis on combat and officer patrols than is the practice in other armies. Members of patrols will frequ ently expose themselves to enemy observation to locate weapons from the fire brought to bear on the exposed personnel. When secrecy is essential, as in the preliminary reconnoitering of a position on which the attack is to come as a complete tactical surprise, the Japanese scout can be as quiet and inconspicuous as the deepest infiltration demands.




SECTION IV - SECURITY.


Security is not emphasized by the Japanese. Their theory is that by pressing a vigorous offensive they will keep the enemy on the defensive, leaving him little opportunity to attack on the Japanese flank or rear. Bivouac areas, rear area installations, and lines of communication are left relatively unprotected, although security in the advance is accomplished through the normal use of advance guards, rear guards, and flank patrols.




SECTION V - THE OFFENSIVE IN THE JUNGLE.



1. GENERAL.

Japanese tactical doctrine is dominated by the concept that offensive action gives a decided advantage in all warfare, and certain modifications were designed to facilitate offensive maneuvers in the jungle, The difficulty of maintaining contact among units in the jungle makes it imperative to decentralize command. The Japanese recognize that the success of the operations of small units depends upon the training and ability of their commanders to function independently. Contact between adjacent units and mutual support are not emphasized. Orders to small and large units are brief; supply and administration details are almost ignored, and general coordination is sacrificed for simplicity to conform to the Japanese concept that the infantry can gain its obj ective solely by offensive action. Where commanders are able to make plans for small-unit operations in detail prior to their execution the Japanese system functions well; but, even in the days of success, excessive rigidity of tactics was apparent, and commanders confronted by unexpected contingencies lacked resource£ ulness,




2. SUPPORTING FIRES OF INFANTRY WEAPONS.

a. Mortars.

Mortars are employed extensively in jungle warfare. In the offensive they are placed well forward to neutralize localities holding up the advance. Targets are engaged with which machine guns cannot deal and for which artillery may be either unavailable or unsuitable. Mortars are used skillfully by the Japanese who are adept at firing a few · rounds, then changing position rapidly. Defensively, mortars are often used to cover probable assembly areas and avenues of approach which the enemy is likely to use.

b. Machine guns.

Machine guns, normally employed in pairs, are placed well forward to support front-line infantry. They go into position under cover, and are usually successful in opening fire accurately and with surprise effect. Positions are selected with a view to ad~ancing as the attack progresses. Forward movement to new positions may be by individual gun, or by pairs, depending on the terrain and the situation, but preference is shown for movement by pairs. It is normal for the guns of the platoon to fire on the same target. Emphasis is placed on close cooperation with front-line infantry, but the guns are not used as a base of fire to the extent practiced by our Army.

c. Antitank guns.

Antitank guns have a primary antitank mission, but in the absence of tank targets they fire on infantry. They are placed in position well to the front and go forward with the advance of front-line infantry.

d. Battalion and regimental guns.

Battalion and regimental guns are assigned the primary mission of neutralizing the enemy's machine guns. They are located well forward and are prepared to move ahead to new positions with the infantry. They, too, are put into position under cover and seek surprise in opening fire. They are prepared to carry out indirect fire missions, and give close support to the .front-line infantry, as do antitank guns and machine guns.

e. Long-range fire.

Although long-range fire of heavy infantry weapons is discussed in training manuals, it is seldom utilized. Most of the heavy weapons are placed well forward, and depend for the accomplishment of their mission on a heavy volume of accurate and unexpected fire at relatively close range,




3. ENVELOPMENT.

The Japanese favor the enveloping attack in the jungle. Often they attempt to turn the hostile flank by the conventional envelopment, particularly when infiltration tactics have not been successful. In such envelopments a frontal attack is usually delivered as a holding action to contain the enemy, and to divert his attention, The frontal action may be conducted on such a scale, however, as to constitute the main attack, aimed at penetr ation of the hostile line to he followed by an envelopment of one or both of the flanks created by the penetration. In the jungle, the Japanese usually employ the close-in type of envelopment. The hostile line is probed for soft spots, often by combat patrols, and particular efforts are made to locate enemy heavy weapons. Often the Japanese fire machine guns to draw the fire of enemy heavy weapons. If such a ruse is successful, the Japanese put down heavy concentrations of mortar fire on hostile heavy weapons, usually timed to take effect just as their advancing infantry are coming within a sault distance of th enemy line. The penetration assault usually is made on a narrow front and often by successive waves.

After the breakthrough of the enemy lines, the assault forces may attempt envelopment of either newly created flank. The flank to be enveloped often is determined in advance of the operation, however, and thus an advantage the opportunity to choose the direction best suited to exploit immediate tactical circumstances is lost. As is done in conjunction with envelopments proceeding from flank movements, secondary atlacks may accompany the attempt at point penetration, usually at some distance from the area designated for the major breakthrough.

In either flank envelopment or envelopment from a penetration, the base of fire is usually established in the aTea of the holding, or secondary attack. The Japanese prefer surprise to adequate preparatory fire generally, since the natural concealment of the jungle often permits attacking units to reach the edge of the enemy position before coming under fire. The commitment of a large proportion of troops to the main and secondary attacks leaves only a small reserve to be used to support the principal attack or to exploit the success of the secondary attack. Reserves, such as are available, are far forward and widely dispersed,




4. NIGHT ATTACKS.

Night attacks are favored by the Japanese, because they can execute such operations without strong artillery support and because they believe the usual Allied practice is to fi ght by day and assume the defensive by night. Night attacks are usually made on narrow fronts and with limited objectives by reason of the difficulties of control, direction, identification, liaison, flank protection, and artillery support. Where po. si hle the fopa_n ese attack uphill. This prevents their being silhouetted against the skyline, and the slope helps Lhem maintain direction. At times units may be leapfrogged through each other to attack deeper o~j ectives. Night attacks may be used only as harassing operations, or to reach and hold objectives which cannot be taken by day. Front-line units are instructed to deploy into the , most advantageous formation; to take advantage of terr a in ru1d cover before assaulting; and to prepare fo r sim ultaneous firing, even if attacks are not directed at the same obj ective. Night attacks are often accompunied by ex essive use of signal flares, and a demon hation-~houting, firing of firecrackers, and clrurnbea tiog-u u·ally is carried out at some distance from the actual point of attack.


5. AMBUSH.

Emphasis has been placed upon the development of the tactics of ambush as being well adapted to the jungle. This device may be either a hit and run tactic used against a small patrol or an operation directed to destroy a platoon, company, or even larger unit. The ambush favors twisting trails, water point, supply routes, small clearings, and streams used for transport. Platforms are built in trees and used as machine-gun emplacements. The ambush is often mounted in connection with a road block.


6. ROAD BLOCKS.

Because of the paucity of roads, road blocks are especially eITective in slowing up the movement of road-bound equipment. The Japanese have established road blocks in rear of the enemy along his line of withdrawal. An enveloping force or raiding party is generally charged with this mission, which is effective in disrupting the movements of the enemy at a critical time. During the Kohima-Imphal withdrawal, the Japanese employed road blocks on a relatively large scale. The terraln and lines of communication lent themselves to this type of warfare. The roads in the area pass over innumerable steep and dense jungle-covered hills; in many instances the roads run along tops of ridges or the sides of hills, and it is not possible to bypass road blocks. In this area road blocks consisted of old car chassis, piles of stones, tree trunks, chevaux-de-frise, demolished culverts, and antitank ditches.




7. ARMS AND SERVICES.

a. Infantry.

The infantry is well armed with weapons suited to the tactical requirements of jungle terrain. Reliance is placed on individual and small unit operations, rather than on mass maneuver. The infantry 1s the basic arm in jungle operations as well as in other types of warfare.

b. Artillery.

Little emphasis has been placed by the Japanese on the use of quantities of artillery. In many instances, mortars have been used as substitutes for artillery, and, at times, to reinforce it. Principles of artillery employment are governed by the desire to maintain close support of the infantry even at the expense of olher legitimate missions. Jungle terrain and weather limit the movement of artillery, though in Burma the Japanese have demonstrated themselves to be advanced in the transport of medium artillery and capable of great speed in the transport of- light artillery. Light artillery is placed well forward and sited for protection. The Japanese use forward observers boldly, often operating well in advance of their forw&rd positions and relying principally on mobility for protection. There is no evidence that the Japanese make extensive use of unobserved fire. Artillery fires are usually confined to prearranged infantry support tasks. If the artillery were placed behind the center of the infantry line, as is the Japanese practice in open warfare, the distance between it and the enemy would have to be increased so that the pieces could deliver high-trajectory fire without danger from shells exploding against treetops. The Japanese therefore site their artillery in the jungle on a flank of the line on which their infantry is advancing. They do not use concentrations of fire in a manner comparable with that of the Allies, though in general the accuracy of Japanese artillery fire is good.

c. Engineers.

Engineers in the jungle are employed in small detachments assigned to small combat teams, infantry battalions, companies, 'or even smaller units. All available evidence indicates that forward engineer units depend on hand tools and equipment. The mission of engineers in the jungle is the same as in other forms of warfare but with some modifications in the techniques by which it is accomplished. In river crossings, although some standard equipment is used, dependence is placed upon expedients. In the use, improvement, and construction of roads, the Japanese consistently follow the practice of making maximum use of available means, but they are not quick at this work.

d. Armor.

In Malaya tanks were used effectively in support of infantry operations. The tanks normally attempted to form a passage for the infantry by frontal attack. If this maneuver failed, the tanks tried to pin down the hostile troops defending the road block while the infantry infiltrated around the road block to attack it from the flanks or rear. As an alternate measure, in relatively open jungle, the tanks themselves attempted the envelopment. More recently, in Burma, tanks were used in support of infantry in attacks on defended perimeters, and in attacks on Allied road blocks. In the majority of cases the attack wa. carried on at night. Defensively, the Japanese have used tanks to stiffen their defensive positions, and, in one instance, for counterattack within a defended perimeter. In general, commitment of tanks has been made in small numbers, and employment has been unenterprising.




SECTION VI - THE DEFENSIVE IN THE JUNGLE.



1. DOCTRINE.

The Japanese reject the passive defense because it gives an opportunity for the enemy to improve his advantage of assembling superior strength in personnel and fire power. Their system of defense is an active one, based upon the principles of surprise, maneuver, and counterattack.


2. MOBILITY IN DEFENSE.

Mobility is attained by the establishment of alternate positions to which the defenders can shift rapidly. Personnel shelters against hostile artillery fire are located close to firing positions so that the defenders can return quickly to the firing line when hostile artillery fire ceases. Raiding patrols, trained in the technicalities of enemy equipment, penetrnte the enemy position to destroy equipment and installations, and to disrupt communications. Mobility is maintained also by the counterattack, a vital part of Japanese defense.




3. SURPRISE IN DEFENSE.

Japanese exploit natural camouflage and the opportunities for siting positions in the concealment of prepared positions in Lhe jungle. Fire and movement discipline is rigid and permits the minimum of activity which would reveal the location of weapons and positions. Usually fire is withheld until the enemy comes within effective range of the least expert Japanese marksman. As in other terrain, the Japanese normally use a forward line of defense in advance of their main line of resistance. The forward line is expected to prevent surprise of the main body, and when contact is made with the enemy, it either withdraws or remains in concealment to harass the enemy from the rear.


4. OFFENSIVE ACTION IN DEFENSE.

The Japanese counterattack in the jungle relies on the speed and shock with which it is launched, rather than on careful planning and artillery preparation. Attacks may be preceded by concentrations of short duration from mortars and grenade dischargers, and are always supported by all available riflemen and automatic weapons. The counterattack is accompanied. by shouting, firing of firecrackers, and pounding of empty oil drum. The Japanese will give up the advantage of prepared positions if they believe the possibility of a successful counterattack exists. The counterattack differs from the general practice of other armies in that it is seldom coordinated wilh activities of other units, and the possibility of its failure is not considered. Since units of all sizes counterattack, the attacking force often consists of as few as eight or ten men led by an officer or a noncommissioned officer. As the attack progresses, however, reinforcements are used to develop the penetration. Because of the difficulties of movement through the jungle, counterattacks are usually local. As a variation of the counterattack, mortar and artillery concentrations are plotted on the Japanese positions and can be laid down promptly if the enemy occupies them or attempts to reorganize near them. These concentrations have been known to make captured positions untenable.


5. ORGANIZATION OF THE GROUND FOR DEFENSE.

Defensive organization of the ground is very thorough. It usually consists of a series of strongpoints, organized in depth and mutually supporting, each one covered from the flanks and rear by riflemen in fox holes and in trees. Defensive positions are selected with a view to their utilization as bases of fire for counterattack. Positions are sited on high ground where possible, and often a series of high points is defended, with no organization made of the intervening ground.

Terrain features are utilized as flank protection and as antitank obstacles. The Japanese usually place their main line of defense on the reverse slope of high ground when the topography and orientation are such as to silhouette the enemy against the skyline as he comes over the crest of the hill. Small outposts cover the best lines of approach up the forward slope. There generally is no outpost line beyond the small parties on the forward slope. Normally, the defensive position is organized for all-around defense. Sectors of fire are allocated to automatic weapons in order to establish a fire net. Riflemen are disposed around these weapons, and the preparation of field fortifications is commenced at once. Machine guns are recognized as the backbone of the defense and are sited both singly and in groups.

They normally are given only a final protective mission; their sectors of fire are extremely limited and generally close in front of the position. Lanes of fire for these guns are cut by tunneling through the underbrush, thus making it extremely difficult to locate them, but at the same time restricting lhe fields of fire. Long range use of machine guns is not practical in the jungle. The guns are usually sited for cross fire; they also may be sited in ravines to deny this route of approach to the enemy.

Extensive use is made of alternate and dummy positiolls, and weapons are frequently moved from one position to another. Organization of the ground is progressive. Starting with fox holes, the positions will ultimately comprise pillboxes for heavy weapons, with several firing ports, and bombproof shelters.


6. WITHDRAWL.

Withdrawal, like defense, is contrary to the Japanese concept of war. Little attention is devoted to it in their texts, and reference is made to it as "retreat combat". Lack of medium artillery properly to cover a withdrawal, and the difficulties of long-range machine-gun fire in the jungle, often result in the sacrifice of the covering force. A training manual states: "During retreat, machine guns do not think of loss, but sacrifice themselves for the army by firing fiercely against strong pressure of the enemy or against the enemy which is of greatest danger to the firstline infantry. They must make the withdrawal of friendly troops easy. Allow no enemy advantage." Yet, in the withdrawal from the Kohimalmphal area, emphasis was placed on delaying action and obstacle warfare, rather than on the last ditch stand and the sacrifice of defending units.




SECTION VII - SUMMARY.


1.
Tactical principles in the jungle do not differ materially from those employed in open warfare. The technique or application of these principles, however, does vary, and the Japanese have taken advantage of this.

2.
The Japanese stress the principle of surprise and employ it in the defense as well as in the offense.

3.
The Japanese are aware of the importance of mobility in jungle operations and have made it a basic principle of tactical planning.

4.
They believe strongly in the inherent advantages of vigorous offensive action, and often attack without adequate preparations.

5.
Deceptive measures are used extensively, and ruses of all types are designed to harass the enemy.

6.
Long-range reconnaissance is thorough and detailed; close-range reconnaissance is good when time permits.

7.
As a corollary to the doctrine of offensive action, the Japanese assume that comprehensive security measures are nol necessary.

8.
Infantry weapons are sited well forward.

9.
Night attacks arc favored by the Japanese.

10.
The Japanese have not made full use of supporting artillery.

11.
Armor is employed in support of infantry operations, and commitment has been in small numbers.

12.
The Japanese organization of the ground and field fortifications is uniformly good.

13.
Japancse defensive dodrine is an active one, employing the principles of mobility, surprise, and offensive action.

14.
The Japanese will counterattack promptly when their position has been overrun, either by fire and movement, or by fire alone.

15. They take full advantage of natural cover and concealment, and thoroughly understand the importance of camouflage.



PART III - COUNTERAMPHIBIOUS AND AMPHIBIOUS OPERATIONS


SECTION I - DEFENSE OF SMALL ISLANDS.


1. TARAWA TO IWO JIMA.

The small islands of the Pacific Ocean arc of two types: coral or volcanic. The coral island or atoll generally consists of oval-shaped islet inclosing a lagoon. These islets vary from a few yards to miles in width and length. Seldom more than 25 feet above sea level, these low flat islands have a high water table, and as a result deep fortifications can be constructed only with difficulty. With the exception of the antitank ditch, all coral island defenses are of the pillbox variety.




Figure 9. General defense sytem on Betio (tarawa). 		Vegetation on these islands is usually coconut palm, mangrove, and pandanus. A coral reef almost completely surrounds the atoll and is the primary defensive terrain feature to be found on the small islands of the Pacific.

The volcanic islands are generally much larger than the atolls. They have considerable elevation, and the terrain. is rugged and mountainous. Areas suitable for amphibious landings are not as common as is the case of the coral islands.

The fringing coral or barrier reef is often present. It is because of the terrain differences of these islands that Japanese defense measures will vary. While the small-island stage of the war with the Japanese has begun to be eclipsed by campaigns involving the movement and maneuver of large forces, landing operations will, of necessity, continue until final victory. It is therefore essential that some consideration be given to Japanese defensive tactics as applied against Allied amphibious operations.

In the early campaigns in the Gilbert and Marshall . Islands the Japanese desire to take the offensive led them in futile attempts to meet the landing party al Lhe licach. They attempted an annihilation before a landing was effected or tried to launch an immediate counterattack before beachhead positions could be consolidated. Perimeter defenses were set up to accomplish this mission. If the defended island was long and narrow, the entire perimeter of the island would not be fortified, but installations would be grouped in the central areas with tank ditches and traps isolating the fortified area from the remainder of the island.



The tank ditch was a most important element in ihe defense plan, for the majority of the pillboxes and other fortifications were located there in the endeavor to keep the attacker from penetrating that line. In both the complete and partial type of perimeter defense the first line of defense was the coral reef.

A menace to navigation, these reefs lie only a few feet below water at high tide. They can be passed over by craft of shallow draft, although sudden changes in the wind, if strong enough, will lessen the depth and thus prevent passage. The Japanese supplemented the natural obstacle of the reef by constructing log barricades, coral or concrete obstacles, barbed wire, and mines. The fundamental tactical concept of the Japanese, Lo meet the invaders at the beach or to launch immediate counterattacks to dislodge them before they had established a beachhead, resulted, in the early island campaigns, in excessive losses from Allied air and naval bombardment.

The fanatical offensive spirit of the Japanese was responsible for committing their defensive works along the beach, or in static perimeter defenses. Noticeably absent in most cases were prepared defensive positions in depth.


Figure 11. General atoll and coral island, showing typical reef development.
Figure 10. General defense sytem on Peleliu.



2. IWO JIMA.


a. General.
The small volcanic island of Iwo Jima was tactically organized in a manner which indicated that the Japanese have begun to apply the lessons learned in their ill-fated defense of other islands. The only suitable landing beaches were on either side of the southern portion of the island. The northern half had a rugged coast line which was not suitable for landing purposes. In the defense of this island the Japanese made a careful evaluation of Lhe terrain and utilized it more effectively than had been the case heretofore.


Figure 12. General defense system on Iwo Jima. 		b. Beach defenses.
The Japanese realized that American landings would be confined to the beaches found on the east and west sides of the southern peninsula. Coast defense and dual-purpose gun emplacements were constructed to cover these prospective landing areas. These emplacements were similar to the concrete positions found at Saipan in which field guns for antiboat and coast defense missions were emplaced. Barbed wire, and mines of the horned and yardstick variety, were used extensively immediately behind the main beach areas.

For the first time, there were no boat and underwater obstacles. Antitank ditches were prepared throughout the level portion of the island and at the beaches to deny avenues of probable tank approach to the more vital installations farther inland. A new beach defensive measure was observed in the use of gasoline drums. Partially buried along the water's edge of the beach, they were regularly spaced in intervals of 15 to 20 yards and in depth from one to three drums.

This type of obstacle presents a number of possible uses. One is to prevent landings by igniting the gasoline contained in the drums through some remote control system, by the use of trip wires, or by using incendiary ammunition from some concealed position. The drums actually found held small-arms ammunition and small explosive charges which could be detonated by electrical control methods.

c. Antiaircraft defenses.
Two airfields were operational at Iwo Jima at the time of the American landing. The entire defense system of the island wa5 predicated upon the protection of these installations. Heavy concentrations of automatic antiaircraft artillery were emplaced around the fields. Dual-purpose guns were concentrated between the airfields and to the north of Motoyama Field No. 2 (see Figure 12). The Japanese employed 25-mm, twin-mount, automatic weapons and also the single-mounted 25-mm and 13-mm guns. It is probable that an improvised mount was adopted for the 20-mm aircraft gun which was used to supplement antiaircraft defenses. Weapons were sited so that they could be employed in a secondary mi5sion against terrain targets of opportunity. Radar stations were well chosen in order to give early warning of the approach of hostile aircraft.



d. Infantry organization of the ground.
It was in the infantry defense of lwo Jima that the Japanese made the utmost use of the natural terrian features found on the island. The entire system was organized with a view lo an all-oul defense of the airfields. The heaviest concentration of infantry defenses was located at these installations and in those areas where landings from the sea were most probable. The northern periphery of the island, by reason of natural defensive features which limited the possibilities of landings, had fewer fortifications, but these were supplemented hy outposts located along the rugged coast line. Pillboxes and entrenchments were organized in depth and so located as to provide an all-around defense, and mutually to support each other. They were constructed of reinforced concrete, being in many instances 4, feet thick, and they were found throughout the entire island. These positions were located so that direcl and flanking fire could be delivered along the beach areas.

Alternate and secondary positions were well prepared. An extensive use of minefields and antitank ditches was made in order to deny approaches to the interior and rear of all prepared primary positions. Terrain features were utilized to the fullest extent in the constrnction of all fortifications. Where the terrain was rocky and rugged, the Japanese improved on existing caves, and, if necessary, constructed new ones in the walls and sides of mountains, volcanos, or hill masses. At I wo, man-made caves 30 to 40 feet deep, were complete with stairways and interlacing corridors and passageways.

In one particular area, 400 by 500 yards, more than 100 of these caves were prepared. Mines were used extensively to supplement the defensive features of these natural or artificial works. Gaps in any defended area were covered with mines, and by the fire of rifles and automatic weapons. In each of these areas a center of resistance was generally encountered. Such centers, too, were organized for all-around defense. Strongpoints emanating from the center wire connected by communication trenches. Generally, a large mobile reserve was maintained for counterattack purposes. The accepted tactics for the employment of these reserves were to launch the attack as soon as practicable, preferably on the night following the landing. If this failed, the counterattacking elements fell back on the high ground and engaged in the traditional fight-until-death type of resistance. In this actual operation only small local counterattacks were made.

e. Antitank defenses.
(1) Antitank weapons.
The Japanese relied on the 37-mrn and the 47-mm antitank gun in the artillery defense plan against tanks. These guns generally were employed from behind tank barricades and ditches. They were emplaced in both open and covered fortifications. Alternate positions were well chosen, and there was an attempt at mobility. The Japanese continued to open fire at shorter ranges than do other armies. Mortars and field artillery weapons also were used in the role of antitank artillery; the use of mortars was particularly effective at Iwo Jima.

(2) Antitank obstacles.
Obstacles and barricades designed to impede the progress of tanks were constructed on all of the small islands taken by the Americans thus far. These obstacles took the form of concrete tetrahedrons, coral cairns, steel rail barriers, and walls of concrete or masonry. Antitank ditches were also an integral part of the defense system. On the coral islands, they were relatively shallow because of the water table, but in filling up with water they became even more effective. These ditches were generally 5 to 7 feet deep and 12 to 14 feet wide. On Iwo, V-type antitank ditches were prepared throughout those areas where tanks would be most likely to travel.

These obstacles were often in the form of short segments of unconnected Trench, and were prepared in a broken Line of egn1enls 20 to 30 feet in length witb a 20 foot interval between trenches.
Figure 13. Rugged terrain defended by Jaoanese at Peleliu.

(3) Minefields.
Increased use of minefields to cover areas not protected by terrain and fire has been made by the Japanese. The practice of laying minefields along the beach apparently has been discontinued. In former island campaigns, the Japanese learned that these fields would be prematurely neutralized by American naval ans aerial bombadment. Now the Japane$e appear to prepare the minefield behind the beach and then. lay the mines just prior to the expected landing and after the Allied bombardment. Depth harges rigged with trip wires have been used. Recently available documents on the defense of other islands reveal that instructions have been issued for the placing of bombs-nose up, fuzed and armed - during the night before the expected landing. A series of empty holes, approximately 500 yards inland from the beach at Iwo, may possibly have been the preliminary preparations for such minefields.



(4) Mortars.
The Japanese made extensive use of mortars at I wo for normal missions and as an extremely effective antitank weapon. Large caliber mortars, probably the Type 98, 250-mm spigot type, were used against personnel and armored vehicles. These weapons had previously been zeroed in on strategic areas, as was the case of other artillery, and fire was concentrated whenever suitable targets presented themselves. The use of mortars at Iwo was more effective than was the case in any of the previous island campaigns and is an indication that the Japanese are applying the tactical lessons of former defense operations.

(5) Field artillery.
The Japanese use artillery in close support of the infantry and normally do not employ it in general support by massing guns. Concentrated fire, according to their practice, often consists of the battalion gun firing in unison with the regimental gun. The fire of artillery weapons, in the small-island campaigns thus far, has been desultory and sporadic. At I wo guns were well sited and delivered heavy, direct, and flanking fire along the beach line and on other vital areas; however, true massing of fire was not used. Covered artillery emplacements were dispersed along the high ground overlooking the beach. Artillery, as was the case with all installations, was organized in depth. Weapons were often emplaced in caves which were then sealed except for embrasures through which fire was delivered. This method of artillery employment made it extremely difficult to locate and destroy the weapons since they were afforded considerable protection from observation and hostile fire, particularly from the sea.

(6) Rocket bombs.
An innovation in defensive warfare reported at I wo was the utilization of a rocket principle in the launching of the 250-kg. general-purpose bomb. No modification is made to the bomb itself, but a rocket containing the propelling charge is attached to the tail assembly.




SECTION II - DEFENSE OF LARGE ISLANDS AND CONTINENTAL COAST LINES.



1. GENERAL DOCTRINE.

In the defense of a long shore line, the Japanese formerly tried to anticipate the general areas in which landings would be made and then organized the most suitable landing beaches, as strongly as possible, with what men and materiel were available. If a landing was made at a defended point, the basic doctrine appears to have been the destruction of the landing party at the beach, or before a consolidation of Lhe beachhead position was possible. If this failed, an all-out counterattack was to be launched, usually on the night after the landing had been made. Obviously, such defense measures were inelastic.

If the landing was made at an undefended point along the coast line, the Japanese attempted to desfroy the landing forces either by counterattacks made by mobile reserves located in central areas or by counterlanding measures. In the Leyte, Luzon, and Okinawa campaigns, their doctrine appears to have been changed. In the place of the old theory of destroying the enemy before, during, or immediately after the landing, the Japanese have adopted as a general plan a defense of rugged ground in the interior of the island.



The selected area is organized in depth for all-around defense. When possible, it appears that this area is chosen in the vicinity of the most likely landing beaches. These beaches are organized defensively to accomplish as much harassment of the landing force as possible without irrevocably committing the main force to p'osition defense or counterattack in the beach area. If the preliminary bombardment is severe enough, the Japanese abandon these positions and retire to the organized defenses of Lhe interior. Within the organized area, the Japanese will retire from position to position only when they are in immediate danger of being cut off. They do not die in their positions if a further defense can be carried out from more rearward positions in the defended area.

It is only when the last positions have been breached that there is the possibility of a final banzai charge. The counteratlack, on the other hand, is used frequently and well, though in relatively small force, as an aid to the conduct of the defense of the chosen terrain. This does not mean, however, that the Japanese have completely abandoned the doctrine of defending at the beach. Rather, there is every indication that they will defend beaches, though less strongly than before, when it fits their over-all plan of defense in depth. The enemy often defended the wrong beaches. Bougainville, New Guinea, and the Philippines are examples of areas in which faulty strategic estimates of landing sites have been made.


2. DEFENSE OF SEA APPROACHES TO THE BEACH.

a. General.
When beaches are to be defended, the Japanese have always been inclined to occupy high ground, and this concept, coupled with the desire for close combat, will decide the natu re of their coast defense system. Where terrain permits, positions are sited on the high ground to the rear of the beach, and reliance is placed on artillery fire from well-prepared and concealed positions. If, however, the ground does not permit this type of a defense, positions may be sited close to the water's edge, and the typical attempt to destroy the invader at the beach is made.

b. Artillery.
Artillery weapons are sited so that they have the maximum fi elds of fire and sight unless concealment and inaccessability of these weapons are considered to be of greater importance. Artillery has generally been zeroed in prior to the landing. At Leyte and Saipan range points were indicated by markers. Use of the fringing coral reef and buoys equipped with flags have been noted in other instances. At Peleliu, the Japanese had weapons, range of which would have made the use of the landing beaches extremely hazardous, a nd perhavs impossible, if they had been properly employed. But iustead of concentrated fire only a desultory hara sing effect was achieved. At Saipan, throughout D-plus one, massed fire was not employed; generally, one gun fired at a time. There seemed to be a tendency to fire at datum or registration points repeatedly.

Range and deflection adjustments in fire seldom were made during firing. This is typical of the dissipation of artillery strength in coastal defense that has made American landings on Japanese-held shores far less costly than they might have been. At Leyte and Saipan some artillery positions were sited for sea and beach defen se purposes only, whereas others had that capability and the additional one of engaging targets behind the beach. Coastal defense guns and the battalion and regimental guns are emplaced Oil the beach if high ground to the rear does not exist.

Large coastal guns form the backbone of the defense system. This heavy artillery is usually found in open emplacements, but concrete, covered fortifications will be encountered when the strategic importance of the locality requires them. The Japanese stress mobility of all artillery but with large weapons, like the 10-cm howitzer or larger which have little mobility. The doctrine is to fortify and camouflage to prevent detection and neutralization by opposing artillery and planes. In these practices the Japanese have achieved a near perfection. Artillery will often be mounted in turrets and on the more elaborate type of carriage. These formal emplacements may be expected to become more common as the advance to the Japanese home islands continuos. These weapons are the typical seatcoast flat-trajectory artillery which will open fire on shipping at extended ranges and then later lay directly on the landing craft as they approach the beach.

Regimental and battalion guns are often used to reinforce the fire of all normal coast and field artillery weapons. They are generally sited in open emplacements and are provided with alternate positions to which they can be shifted should the action dictate. Dummy positions are constructed with great care and have been responsible for attracting the fire of the invading troops. However, the unpredictability of the Japanese often causes them to emplace these weapons close to the highwater mark of the beach. Such was the case at Cape Torokino on Bougainville Island.

Extensive use is made of caves and coral cliffs, and other natural recesses. Complete concealment, and invulnerability to attack from land, sea, and air are striven for in this manner. Fields of fire and mobility are often sacrificed in the desire to achieve concealment. In one instance, at Saipan, an artillery piece was kept in a cave that had steel doors for protection. The piece would be run out, fired several times, and then withdrawn back into the cave. It is obvious that artillery employed in such manner will have a limited field of fire.

At Saipan, Japanese mortar fire was effective, but the failure to mass fire again prevented a more advantageous use of this close-support weapon. Mortars are used against frontal targets such as landing craft. Often sited behind the first available defilade, fire is directed by observers on adjacent high ground.

c. Land-based torpedo emplacements.

The possible use of land-based torpedo batteries in a coast defense mission has been indicated. These installations will probably be encountered in areas close to the Japanese homeland. The torpedoes may be launched from emplacements located at the water's level, or from batteries sited below sea level constructed as part of an elaborate tunneling system. In such cases, the torpedo is probably fired in the same fashion as employed by underwater craft.




3. DEFENSE OF THE BEACH.


a. Landing barge and tank obstacles.
As emphasis on beach defenses has declined, less attention has been paid to the use of obstacles. Obstacles constructed on the beach or in adjacent water have been of two types: those that hinder landing craft, amphibious vehicles, and tanks; a·nd those that attempt to destroy them. Shore line obstacles, when used, are constructed with the least possible manpower from local materials. Where a reef exists, obstacles will often consist of steel or concrete posts and corallog barricades. If there is no reef, wide ditches are dug along the beach, or natural features, such as creeks and other water courses, may be improved upon. A new trend has been observed in the construction of antitank strongpoints sited about 400 yards apart. These strongpoints have a frontage of 150-200 yards and consist of trench and pillbox systems completely enclosed by an antitank ditch. Each strongpoint is independent with its own artillery and machine-gun emplacements. Additional antitank ditches run back inland from the sea di- ' viding the whole area into sectors. Antitank ditches are usually 16 feet wide and 6 feet deep. It seems apparent that where the beach is defended antitank protection becomes the key note of the whole defensive system. On the beach at Leyte, antitank barriers were constructed by imbedding two or three heavy coconut logs which were lashed together in staggered rows. Antitank barriers were then flanked at both ends by antitank ditches.

b. Antipersonnel obstacles.
The purpose of antipersonnel obstacles, according to the Japanese, it to obstruct the invader's advance, and, when combined with fire power, to destroy him or hinder his movements and further to prevent a surprise attack. To accomplish this mission, the Japanese use a variety of obstacles. Wire fences of singlestrand type are commonly used. Double-apron entanglements have been reported, and concertina wire has been used. Natural material often supplements the wire. Sharpened bamboo and wooden stakes are interspersed between rows of barbed wire. Antipersonnel barriers of this nature were used at Leyte. High walls and barricades of logs and stone are other means used to impede the advance of the infantry. Snares and trip wires of single-strand barbed or smooth wire, pegged into the sand of the beach, hindei· the pass;lge of troops. Laid out in the pattern of minefields and often ernplaced below the high water mark they constitute a serious obstacle for troops wading ashore.

c. Mines and minefields.

1) Underwater
mines. The Japanese have occasionally made use of mines underwater on the coral reef fronting the defended beach. Generally, they are of the single or double horned variety. In many cases, the mines are connected in tandem and tied into an existing barbed-wire entanglement. Antitank mines are oflen laid in shallow water, and a few floating mines have been encountered. Many of the underwater mines employed at Saipan did not detonate upon contact, probably because of an excessive exposure to salt water. The warning given to the invader by these duds as to the possible existence of other mines renders such defenses more than useless to the Japanese.

(2) Mines along the beach.
In the early island campaigns the Japanese use of mines along the beach was often haphazard and faulty. Recently, however, a marked improvement has been made both in the siting and camouflage of this defensive weapon when it is used on the beach. Approaches to antitank barricades and detours around ditches are often mined. Mines are used to protect pillboxes in the areas where their fields of fire are limited. Usually, the mines are laid in rows with intervals of a few feet to 10 yards between rows. Mines in a single row may be from 10 to 30 feet apart. At Saipan, single-horn type mines were used extensively along the beach. These mines were laid at 5-yard intervals about 20 yards from the water's edge. Several of the mines were booby-trapped and all were in plain view. Mines emplaced along other beaches did not appear to follow any particular pattern.




Figure 14. Typical Japanese organization of a beach position.. 		(3) Mines beyond the beach.
In the area just beyond the beach, the Japanese have utilized a variety of explosives in their attempts at mine war• fare-aerial bombs; depth charges; and tape measure, magnetic, and yardstick mines. Many of these are booby-trapped and some attempt at concealment of these fields has been made. The majority of these mines have been fairly easy to detect and neutralize. As was the case on the beach, land mines are used in conjunction with pillboxes and obstacles, and in some instances these minefields are covered by enemy fire. However, the general tendency has not been to utilize this formidable weapon of defense to its fullest extent.


4. CONSTRUCTED DEFENSIVE POSITIONS.

a. General.
In all of the island campaigns thus far, the Japanese have constructed a variety of fixed defensive positions. Originally a part of perimeter defenses and later organized in depth, these installations have been built with considerable ingenuity and ability. Wherever possible they are made strong enough to withstand artillery and naval bombardment. Pillboxes, emplacements, and other strongpoints are often arranged in an integrated defensive system wherein each position is afforded mutual fire support, and local counterattacks are covered.

The construction of a complete defense system is a continuing and progressive process, Fox holes, joined by communication trenches and supplemented by rifle pits and machine-gun emplacements, are given a priority in the construction program. The more formal fortifications such as pillboxes, blockhouses, covered emplacements, and shelters then are built to complete the defenses of the area.

b. Passive defense measures.
(1) Camouflage.
Examples of Japanese camouflage have been encountered in all of the island campaigns thus far. Some fortified positions have been camouflaged with such skill and attention to minute detail that they have been extremely difficult to detect, Correspondingly, some attempts at concealment through camouflage have been quite primitive, with camouflage discipline leaving much to be desired. Much 1.se is made of natural material indigenous to the locality of the defended area. Coconut fronds, dune grass, and turf are employed extensively. Vines, creepers, and brush are allowed to grow over positions thus causing a natural blending with the surrounding terrain.

Artificial camouflage such as nets, matting, screens, and disruptive painting are other passive defense measures taken in order to conceal positions. Nets are arranged to conform with the contours of the terrain and are made of a variety of materials such as wire, twine, straw, or fiber. Vegetation is woven into the net to complete concealment. When paint is used to make an object blend with the terrain, the colors u$ed generally approximate the predominant colors of the terrain, or may be somewhat darker. Paint is employed in connection with the over-all natural-cover measures of camouflage. In disruptive painting technique, the Japanese have not achieved the excellence which has characterized other methods of camouflage employed by them. Strips of varying width have usually been painted roughly parallel to buildings but these have generally been easy to detect. On Makin Island, deceptive painting on the roofs of buildings was used to effect blending with the terrain, and all heavy artillery was disruptively painted in red, yellow, green, and blue.

(2) Dummy positions.
The Japanese construct dummy positions in order to draw fire away from vital installations. Genepll y, the localities chosen for these dummy positions have been logical, yet often, however, the failure to impart a sense of activity by occupying these areas has caused quick disclosure of these attempts at deception. Coconut logs, scrap lumber, and material which is available in the immediate area are used in the construction of these installations. Some of the positions encountered thus far have been quite noteworthy. At Saipan, a dummy searchlight position, together with figures of the crew supplemented by a dummy defense gun and a range finder, created the illusion of an important ground installation,



5. COUNTERATTACKS.
Defense at the beach, as in other defensive operations, is considered by the Japanese as a temporary phase which is to be terminated as quickly as possible by reverting to the offense and annihilating the invader. Their doctrine, therefore, calls for their main infantry and tank forces to launch counterattacks as soon after the hostile landing as is practicable. The personnel for these operations are drawn from mobile reserves, and in the conduct of the attack the Japanese place their reserves farther forward than is considered to be valid practice in most modern armies. Stralegic points which mighl possibly be used by the invader are chosen as objectives of the counterattack. Where the terrain behind the beach is more than 50 feet in height, the Japanese troops will concentrate there, leaving the heights at the favorable moment to launch the attack. The object of the attack is to close with the enemy and to destroy him by close assault means such as small arms fire, the use of hand grenades, and hand-to-hand combat. In the past, the Jnpanese have frittered away their available reserves by launching series of small, hopeless counterattacks which were little more than banzai charges. At Peleliu, however, their application of the counterattack differed in that the men were not wasted in uncoordinated and valueless counterattacks but generally were used in operations which showed evidence of careful thought. Where the Japanese cannot mass a large force for the counterattack, they rely on small units to carry out surprise attacks by infiltration methods. Attempting to utilize night or bad weather conditions Lo hide their movements, these forces try to attack and destroy enemy headquarters, artillery, supply dumps, tanks, and, if possible, to kill key personnel. These small-scale attacks have generally res ulted in excessive losses to Lhe Japanese in comparison with the resulls achieved. In line with the recent trend away from defense of beach areas, counterattacks against the beachheads have been infrequent of late (1944).


6. COUNTERLANDINGS.


a. General.
CoU11- terattacking from the sea is a recent development iQ Japanese defensive tactics. Counterlandings have been made in those areas where a landing had been made, unopposed because the length of the coast line precluded Japa nese defense against the landing. Such counterla ndings also have been made against beachheads which have been esta blished by the invader despite Japanese defensive preparations.

b. Counterlanding units.
These units arc apparently formed with the infantry regiment as the base; they are used in opera Lions of a fairly large scale, with the primary mission of destroying the beachhead. Designed to embark from a quiet sector of the coast in such craft as are available, they proceed under naval escort to the site of the enemy landing and, in turn, land in the enemy rear. The basic prin c iples underlying the employment of these units are mobility, surprise, night action, aud lrnnd-to-hand combat. Such tactics require the utmost in traini.i; , timing, and tactical knowledge of the invaders' situation. While the possibility of a successful employment of these forces is not great, there is every possibility that an increase in their use will be made in future operations.

c. Amphibious assault and infiltration units.
This type of counterattacking unit is generally of company size, having three combat platoons whose training emphasizes hand-to-hand combat, infiltration, and amphibious guerrilla assault. Their primary mission is to attack key positions of the beachhead, such as command posts, vehicles, guns, and supply clumps. They are capable of only a limited action and must depend on secrecy and surprise in order to reach their objectives. Quantities of demolition materiel and explosives are carried, together with the weapons of close-assault tactics. At Peleliu an amphibious landing unit, made up of engineers, planned to land its boats with the last wave of American craft. Dusk and the natural confusion of such an operation were to be utilized to the utmost. The barges of sea transportunits. were to be organized and equipped as torpedo boats to attack and destroy American troop and supply craft approaching the beachhead.

d. Swimming assault units.
Another innovation by which the Japanese attempt to oppose lading operations is the use of units generallyof platoon size, composed of powerful swimmers whose mission is to attack and destroy landing craft. These units apparently operate in one of two method. In theory,

- They swim underwater toward the approaching boat and then throw grenades having a 4 or 5 second delay.

- Another method is to swim toward the landing craft, pushing antiboat mines before them until contact is made with the oncoming craft. The mines are of the horn type are are wired to wooden frames.



SECTION III - JAPANESE AMPHIBIOUS OPERATIONS.


1. GENERAL.
The Japanese have not launched an amphibious operation of any considerable size since 1942. Landing operations, thus far, were conducted by the Army and Navy in joint cooperation.

Training for these assaults was thorough, and the Japanese carefully rehearsed all of the details of the impending landing on and along coastal areas whose terrain was as similar, as was possible, to the locale where the invasion was to be made.




2. ACTION BEFORE THE LANDING.
Japanese have adhered to the doctrine that surprise is of paramount importance. Convoys were sometimes divided at sea and approached the objective from unexpected directions. Escorting naval vessels often preceded the convoy it approached the destination to screen it from observation.

In the rigid reliance on the element of surprise, prelanding bombardment by air and naval units usually has been dispensed with. This was probably the case in the action at Kota Bharu, on the Malayan Peninsula. However, omce the Japanese determined the extent of the defenses there, they concentrated naval gunfire on the area and quickly reduced the garrison.

Aerial and naval bombardment, however, has been used to neutralize the air and ground installations of the defender in a few instances. Reconnaissance in such operations was extensive and was made with as much secrecy as possible. Airplanes, submarines, craft of local civilians, fifth columnists, and spies were only a few of teh information gathering meas or agencies employed. Paratroopers have been dropped behind the beachhead to demoralize or destroy the defender and to seize vital installations such as airfields, road junctions, supply depots, and the like.


3. ACTION DURING THE LANDING.

Generally, the landing has been so timed that the first elements hit the beach just before dawn. Bad weather often has been an ally of the Japanese, since periods of storm, rain, and thick fog commonly were chosen in order to achieve greater surprise. Simultaneous attacks were made at several points along the coast line in order to conceal the location of the main effort.

Figure 15. Organization of Japanese landing force. 		When the ship-to-shore movement commenced, all landing craft attempted to get underway at the same time. The flanks of each boat wave were generally protected by armored barge units.

Underwater obstacles were removed by special debarkation work units, while obstacles ashore were removed by demolition units carried in each boat. The initial landing forces generally consisted of the infantry, some field artillery, engineers, and light armored units. Patrol craft armed with automatic weapons gave close support to the landing. Air and naval support continued throughout the action if this additional ...