Japanese Warfare in Burma, Intelligence Bulletin, July 1944 (Lone Sentry)

1. DEFENSIVE POSITIONS

In recent months the Japanese have increasingly been emphasizing the necessity for constructing more, and deeper, communication trenches to connect defensive positions. Emphasis also has been placed on constructing individual shelters strong enough to protect personnel from bombs and artillery shells. "The usual tactics of hostile forces," according to a Japanese source, "are facilitated if our individual shelters and slit trenches are constructed separately."

The same Japanese source states that "communication trenches (deep enough for a person to traverse in a crouched position) between shelters are absolutely essential. Communications during an attack are extremely important, and if communication trenches have not been prepared, intercommunication is impossible."

A U.S. observer recently commented as follows on Japanese defensive positions:

In this area the enemy uses many communication trenches. These vary from the crawl type to those deep enough for a man to walk upright. The depth apparently depends on the time available for digging. The Jap here, as everywhere, is a continuous digger, and, given time, he constructs very elaborate defenses.

The most interesting thing about some of these trenches are the holes dug into the sides, big enough to permit a man to crouch. In such a hole, dug into the side at the bottom of a trench 5 feet deep, a man has complete protection from all types of fire. Not only is this type of shelter provided in trenches, but a large number of individual foxholes have offsets dug at the bottom in the same manner. A few of these had been enlarged enough to permit a soldier to lie down and sleep—in a sort of slit trench 4 feet underground.

In the case of one underground shelter observed, the entrance began at the bottom of a trench and extended straight down for 10 feet. It was necessary for the Japs to use a ladder to get in and out. At the bottom of this "well" [entrance], a short tunnel led to an underground room, which was roughly 6 feet wide, 8 feet long, and 3 feet high. The ceiling, walls, and floor were completely lined with split bamboo. As though the 15 feet of earth were not sufficient cover, the room was placed directly under a thick clump of big bamboo trees. This particular system of trenches contained a number of these deep shelters, all of which were lined with bamboo.

A Japanese training memorandum stipulated that positions be organized in depth, but that the interval between positions must be short enough to permit measures against hostile infiltration. The memorandum stated further:

In constructing positions, it must be remembered that the jungle does not afford permanent shelter; it may be cleared away by bombing and shelling. Deployment must be carried out laterally and in depth, and preparations must be made just as if the ground had been cleared previously.

On terrain which slopes down toward the hostile forces, it is best to place defensive positions between 20 and 30 yards below the crest line—because shells generally will either go over the crest or fall short on the slope.

As a rule, the ground in front of positions should be cleared a distance of 50 yards to facilitate observation and firing... It is essential to keep all positions fully camouflaged. And maintenance of a dummy position close to the front of the main position is a profitable way of observing hostile firing.

2. DEFENSE AGAINST ARTILLERY

In Burma the Japanese have made little use of artillery firing for counterbattery purposes. In the isolated cases where it has been used, the firing has been inaccurate and not concentrated. It is believed that this firing was only for harassing purposes.

As their primary counterbattery measure, the Japanese have used infantry attacks on gun positions.¹ The following are examples of how these attacks were conducted:

a. Twenty to 30 Japanese infiltrated through British infantry posts, and, from a small hill, attacked four artillery sections at night, firing machine guns sighted on fixed lines and firing grenade dischargers. The attack ended with a bayonet charge, which was repulsed.

b. A battery of four guns was in a position where one gun was slightly separated and not visible from the other three sections. At night about 20 Japanese attacked the one separated gun section with grenade dischargers and a bayonet charge. The attackers were armed with explosive charges with which to destroy the piece. After neutralizing this single section, the Japanese attacked the three remaining sections but were driven off.

c. A Japanese soldier crept up through the jungle at night and was in the process of attaching a sticky grenade to a gun tube before he was discovered and killed.

3. OFFENSIVE TACTICS

The following information about Japanese offensive tactics was extracted from an enemy training memorandum:

The interval between hostile [British] positions are relatively long—75 to 100 yards—and there are many places loosely guarded, especially in the rear. Therefore, it is easy to infiltrate into the hostile positions.

In making an infiltration attack, as many grenades as possible should be carried. About 10 men are needed to attack each position, but these should be deployed as much as possible. If more than 10 men are deployed, it becomes difficult to maintain silence, and the lack of freedom for movement leads to heavy losses.

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At each of his centers of resistance, the enemy [British] will be confused by a squad, or less, which will hurl grenades from the flanks and rear; the position will then be penetrated by an immediate assault with cold steel...

¹In this connection, reference may be made to Intelligence Bulletin, Vol. II, No. 4, pp. 13-16, "How Japanese Raiders Demolish Artillery."