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"How Japanese Defended Hilly Jungle Country" from Intelligence Bulletin, March 1944

[Intelligence Bulletin Cover]   The following is a report on Japanese defense tactics in the hilly and mountainous jungle terrain of New Guinea during WWII as reported by U.S. observers. The article originally appeared in the March 1944 issue of the U.S. Intelligence Bulletin.

[DISCLAIMER: The following text is taken from the U.S. War Department Intelligence Bulletin publication. As with all wartime intelligence information, data may be incomplete or inaccurate. No attempt has been made to update or correct the text. Any views or opinions expressed do not necessarily represent those of the website.]




The following notes on Japanese warfare are based on the experiences of United States officers and enlisted men while fighting the enemy in the hilly and mountainous jungle terrain of New Guinea. While these notes should not necessarily be regarded as Japanese tactical doctrine, they should be helpful to United States forces who may meet the enemy on similar terrain in the future.

Generally speaking, in this campaign the Japanese were highly defense-minded except for a few local counterattacks, which were usually staged by a platoon or company. On one occasion the enemy dispatched a raiding party of 100 or more men to infiltrate through the United States lines and demolish artillery positions. The mission failed, with considerable loss to the enemy, after a night-long fight.

As a rule, the Japanese patrolled very little during the campaign, and seemed content to remain concealed in defensive positions or to stick close to their supply trail.

Most of the Japanese troop movements, reliefs, and withdrawals were executed at night; usually about an hour before daybreak.


The Japanese, in this campaign, were frequently careless with regard to security measures. Along their rear trails, they tended to move freely, and with little or no security. United States patrols could often hear enemy groups talking and jabbering several hundred yards away.

Many instances were reported in which Japanese sentries were caught asleep or dozing. Many small outposts of four to eight men were discovered in huddles without lookouts, and groups of two or three walking unarmed along trails near their positions were often taken unaware by United States patrols. When caught off guard under such circumstances, the Japanese were slow to react; they frequently stood or sat for 10 to 15 seconds without moving.


Observers agree that the Japanese did a tactically sound job of selecting and organizing defensive positions. They organized many high ridges, access to which could be gained only by single-file movements. Such ridges, or knolls, were organized with deep dug-outs for the protection of personnel, and were connected with weapon emplacements by tunnels or trenches.

The emplacements, featuring a generous supply both of light and heavy machine guns, were so well camouflaged that often they were visible only at distances of from 5 to 10 yards. The weapons were sited for cross fire at short ranges along the knife-edge ridges which connected positions.


As had been reported in other campaigns, the Japanese were tenacious in the defense of dug-in and protected positions.

In defending organized positions, the enemy primarily employed grenade dischargers, hand grenades, and machine guns. The latter were usually fired down prepared lanes, and rarely were used for traversing or searching fire. As a rule, the enemy withheld his fire until United States troops were within 10 to 30 yards of his position.

The Japanese usually employed their mountain guns singly, and more than two guns rarely engaged a target at the same time. In these exceptional cases, only a few rounds were fired at a time.

It is interesting to note that in the hilly and mountainous country most of the enemy snipers were found on the ground—comparatively few in trees.


To cover withdrawals from organized positions, the Japanese often fired a large number of mortar shells during the night or just before dawn. They also left the barrels of rifles and machine guns sticking out of emplacements to make it appear that the latter still were occupied.


The Japanese almost invariably counterattacked when driven out of a position, and when forced to give up terrain vital for the protection of their rear or their supply lines. These attacks were usually made at dusk or shortly after darkness.

As a rule, the Japanese counterattacks were accompanied by wild firing of machine guns and rifles, and by howls, screams, and other noises. The apparent purpose of such tactics was to frighten United States troops, draw rifle and machine-gun fire in order to locate our positions, and to cover the main attack. The latter usually was made by stealth from another direction, with the Japanese crawling as quietly as possible with fixed bayonets to our emplacements or foxholes. Sometimes the enemy tossed grenades at our positions before assaulting with the bayonet, and on other occasions they stormed the positions in waves, led by sword-brandishing officers giving commands. Also, in a few instances, 30 to 40 Japanese made daylight bayonet attacks by simply rushing our positions. The number of attacks at night varied from one to nine. Intervals between each attack varied from 30 minutes to 1 hour.


The Japanese left very few booby traps, and these were crudely constructed.

A few grenades, with their fuzes adapted for instantaneous activation, were found buried in emplacements and tunnels. These grenades projected about 1/2 inch above the ground. The door of one captured truck was wired on the inside to a grenade.


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