Lone Sentry: Some Defense Techniques Used By the Japanese (U.S. WWII Intelligence Bulletin, November 1943)

1. AS SEEN BY OBSERVERS

Particularly in some of the less active combat zones, the Japanese do practically no moving about during the daytime, and do no firing until attacked. These tactics, plus excellent use of alternate positions, help the enemy to achieve surprise whenever day attacks occur.

Almost all enemy positions in certain areas of level country were dug deep into the ground and were mutually supporting. Back of these positions the enemy sited a large number of mortars. The crews for these weapons apparently determined in advance the exact range to the dug-in positions. And after United Nations forces had assaulted these positions and had taken over part of the area, the Japanese mortars opened a terrific barrage. The enemy soldiers still occupying dug-in positions lay low until the barrage stopped and then counterattacked.

Revetments, either of logs or concrete, were constructed at night around some Japanese positions as a protection from artillery fire.

In the jungle the enemy frequently digs observation posts close to our own positions, primarily to prevent our forces from infiltrating into the area they occupy.

In some areas the Japanese open fire with mortars, machine guns, and rifles immediately after our forces start an artillery or mortar barrage, or a concentration. Part of this enemy fire is trained on areas from which it is suitable for our troops to launch an infantry attack, and part of it is laid down on fixed lines.

2. ACCORDING TO DOCUMENTS

The following extracts on Japanese defense tactics were taken from translations of Japanese documents:

Only to defend is not enough; always to attack is going too far. Even in cases where our mission is only to defend, if we fall into a purely defensive attitude, we will not have enough men, no matter how many thousands may be available. In such cases we would suffer great losses because the enemy [United Nations], with insufficient forces to assault us, would undertake to destroy us by artillery fire alone. To rest on the defensive is death.

When the hostile forces come, you must smash their offensive organization with a brisk, vigorous attack, and instill fear in them. Then they will keep their distance. On such occasions you must withhold reserves for counterattacks, and at the proper time these must be directed against the rear flanks of the hostile forces.

When hostile reconnaissance units encounter our positions, they will first start a searching fire with automatic weapons. You must not return this searching fire, because such action would give away additional positions.

In the jungle the enemy [United Nations] attack usually begins with automatic rifle fire. Since the effective range of these weapons is about 50 yards, we can control their fire by cutting 50-yard-long fire lanes in front of our positions.

Even when we fire at night, the hostile forces return the fire with trench mortars. Therefore, it is a good idea to change the positions of heavy weapons immediately after they are fired. For this purpose, always have alternate positions ready.

It will be advantageous if we can draw hostile fire with dummy positions, false defensive structures, and dummy soldiers.

Since it is easy for the enemy [United Nations] to outflank us in the jungle, it is well for us to break up their movement, or to frustrate their plans by changing our positions.