1. GENERAL

A reliable Japanese source states that the two chief aims of defense consist of:

"a. Overcoming a numerical weakness of personnel by advantageous use of terrain, by establishing suitable fortifications, by making exhaustive battle preparations, and by

"b. Rushing the hostile forces by the simultaneous use of fire power and the counterattack."

The primary function of fortifications, according to the same enemy source, is to enable the proper development of fire power and the accomplishment of other battle duties. The protection of personnel, weapons, and so forth from hostile fire is a "secondary" purpose of fortified positions.

Japanese stress on aggressiveness in defense was demonstrated on Betio Island. In numerous instances, Japanese soldiers, after having been driven from positions, returned to them after U.S. troops had failed to destroy the positions or to guard or occupy them.

2. USE OF FIRE POWER

During the height of operations in New Guinea, the Japanese issued the following instructions regarding fields of fire:

Observers in the Burma theater of operations report that the Japanese seldom open fire from their defensive positions unless an assault is actually made against them. Individual enemy riflemen, in trees or under the roots of trees, are given the task of dealing with hostile reconnaissance patrols which approach close to the positions. The Japanese do nothing that would prematurely give away the location of an automatic weapon.

The enemy usually holds his fire until assaulting forces are from 30 to 50 yards from his positions.

3. COUNTERATTACK

Japanese counterattacks from defensive positions are usually made by small groups, and are preceded by a shower of grenade-discharger shells. The maximum personnel generally used are an officer and 12 men, and automatic weapons furnish most of the fire power. These attacks are launched within 10 minutes after our forces penetrate an enemy position. The Japanese either attack from the rear of a position our troops are assaulting or from a neighboring position—the latter is less likely. In any case, the effectiveness of the attack depends upon the speed and surprise with which it is made.

On a New Georgia front, Japanese forces launched a total of five counterattacks, one of which came at night. In the night attack, the enemy largely employed grenades, which possibly were fired from grenade dischargers held in an almost horizontal position. The daylight attacks were characterized by intense and sustained automatic fire, waist high. In one attack, after failing to locate any flank due to our all-around defense, the enemy used grenades and machine guns to clear the undergrowth sufficiently to reveal our positions.

4. ANTIPATROL MEASURES

A report from the Burma theater describes the following measures the Japanese have taken against opposing patrols:

a. The enemy sometimes dug positions, and left them empty (but covered by men hidden nearby) in the hope that hostile patrols would become curious.

b. The enemy often placed very fine trip wires across jungle tracks leading to his positions. These wires usually had tin-can alarms attached to them.

c. Japanese sentries, posted forward of positions, made a practice of withholding their fire at the approach of hostile reconnaissance patrols until they were certain of the situation. (Many such patrols, owing to this practice, were able to locate the Japanese positions and get away.)