Defense Against Airborne Forces, Intelligence Bulletin, December 1943 (Lone Sentry)

1. INTRODUCTION

Some Japanese tactical plans for use against airborne forces are presented in an enemy treatise which is paraphrased below. The document outlines the tactics that hostile airborne forces are expected to use, and then discusses countermeasures planned by the Japanese.

2. GENERAL

The Japanese believe that airborne forces are most vulnerable to ground attacks from the time their transport planes [and gliders] arrive over the landing area to the time when these forces complete their assembly for combat. A well-coordinated attack by the defenders during this period is the "key to victory," the enemy document states. Other important defensive factors include thorough reconnaissance and security measures in advance, to prevent surprise attacks, and the establishment of perfect communication and liaison between various units of the defending forces (especially in the case of air-ground communications and liaison).

Regarding the plan of attack by United Nations forces, the document reads:

In connection with landing operations by ground troops, the opposition [United Nations] may dispatch airborne troops inland for the purpose of capturing important military points, key communication centers, and important military installations, such as our airfields or other areas suitable for landings.

Thus the hostile forces will try to gain the initiative at the beginning of the landing operations. To maintain this initiative as the operations progress, the opposition, by close coordination with its ground fighting, may try to throw our rear into confusion by use of airborne forces: to cut lines of communication (especially transportation routes and communication lines), to interrupt troop movements, and to destroy command and liaison systems. Or, the enemy may use airborne troops in the areas where their ground forces are fighting, in an effort to make a decisive attack immediately.

To arrange successful countermeasures to the above tactics, it is necessary that our commanders be certain in their judgment of where and when the hostile forces will attack.

It is also necessary that commanders be prepared to engage small numbers of hostile airborne troops who may be landed in the interior [of an island or a considerable distance back of the major ground operations] for the purpose of throwing the inhabitants into confusion. Our forces should look for any change in the attitude of the inhabitants [as a means of detecting whether or not they may be hiding hostile troops].

3. PREPARATIONS

a. General

Regarding Japanese preparations for airborne attacks, the enemy treatise reads:

The commander of the security detachment must work very closely with all units concerned, especially the air units, in detecting hostile plans and in disseminating this information. The commander will strengthen security measures in accordance with intelligence gained from air reconnaissance and from various intelligence reports and observations.

The security-detachment commander will bear in mind that hostile forces will often land at dawn or at dusk, and that first of all, they will usually make a thorough reconnaissance, establish a detailed plan of attack, and execute strafing and bombing attacks.

Because of this hostile reconnaissance, the security forces must try to conceal themselves completely against air observation, and, when the strafing and bombing starts, must fight back fearlessly and courageously.

In seeking concealment from the air:

(1) Use forests, buildings, and so forth, and their shadows as well;

(2) Cover with camouflage nets the positions which are exposed; and

(3) Disperse troops and execute movements rapidly if the orders above cannot be complied with.

It is especially necessary for security-detachment commanders to keep communication facilities in good order so that there will be no hitch in troop movements during an emergency.

The security-force commander will arrange for construction of defensive positions in areas suitable for airborne landings and in the vicinity of vital points which hostile airborne forces may try to capture. The commander also will make a proper tactical distribution of antiaircraft units and of other troops necessary to the defense.

Suitable places for hostile landings are:

(1) Airfields and terrain suitable for aircraft landings;

(2) Flat ground which has few, if any, obstacles;

(3) Roads without obstacles;

(4) Terrain on which planes can taxi; and

(5) Bodies of water which can be used by seaplanes.

If the security-force commander feels that the enemy [United Nations] is planning an airborne attack in a particular area, he will strengthen its defenses by concentrating tank units there, as well as other additional troops. Their advance will be concealed from air observation.

Preparations must also be made for hostile "hit-and-run" attacks. (In these attacks enemy troops expect to be removed by planes after accomplishing their mission.)

b. To Defend Airfields

Regarding security measures for airfields, it is necessary to guard each airfield and its perimeter, as well as the planes and installations. Preparations must be thorough. A careful check must be made on civilians going in and out of the airfield. Security measures must be especially strict at night.

The distribution of the airfield security force may vary according to its strength, the enemy situation, and the adjoining terrain. However, strong means of security must be placed near the planes and the more important installations.

In making the proper distribution of security forces at airfields, it is necessary to place antiaircraft observation sentries at the required points and to have adequate patrols to make rounds through the areas adjacent to the field.

The defense measures will also include the skillful utilization of terrain and other natural objects; the construction of barriers, positions, and so forth; and the establishment of adequate communication with nearby units.

In areas suitable for airfields or runways, it is necessary to place obstacles, or otherwise make it impossible for hostile airborne troops to use these areas. It is best to use such obstacles as wagons, barrels, and boxes, because they can be removed quickly in case our own aircraft need to use the areas.

In keeping watch over the civilians going in and out of the airfield, it is necessary to check their movements carefully and to inspect their clothing and anything that they carry. Individual civilian movements will be prohibited. The internal situation [regarding civilian inhabitants] will be investigated, and if necessary, communication with the outside will be stopped. It is especially necessary to take constant precautions concerning the movements of civilian families.

With regard to tactics that the Japanese may use against airborne troops, the enemy document says:

4. COMBAT TACTICS

a. General

When hostile transport planes get within range, we will first concentrate antiaircraft fire in an effort to destroy airborne troops While they are still in the planes, or while they are parachuting down. From the time of landing, the fire of artillery, machine guns, rifles, mortars, and grenades will be used against the invaders. Before the hostile troops are able to concentrate their strength, the rifle unit [or units] will make a quick, determined assault, and the tank unit, coordinating with the riflemen, will attack and crush the opposition.

Combat tactics against airborne troops which have been able to concentrate in a landing area corresponds, in general, to ground combat tactics. Appropriate movements by tanks and other mobile units are especially valuable for this type of fighting.

It is necessary to annihilate the hostile troops before reinforcements can arrive by air or overland.

Since hostile planes usually will continue to support airborne troops after their landing, it is necessary for our antiaircraft units to resume antiaircraft fire immediately after the hostile troops have landed—except in unusual circumstances.

Since the attacking airborne troops—especially paratroopers—will attempt to use the transportation facilities, weapons, and equipment in the landing area, we must take the necessary countermeasures.

In case of a surprise attack, precautions will be taken so that secret documents and matériel will not fall into hostile hands.

b. Against Parachute Troops

Parachute troops generally jump when the speed of the transport planes is approximately 135 miles per hour and when the altitude is about 450 feet or more. The jumping is completed within 20 to 30 seconds. During this period the parachutists are easy targets for the various antiaircraft weapons, including machine-gun and rifle fire.

While descending, parachutists carry only such weapons as pistols and grenades. For their full equipment they must rely on reaching packs which are parachuted down separately. Therefore, they are weakest from the moment they near the ground to the time they are able to reach their equipment and get ready for action. During this time it is essential that we launch an especially fierce and daring attack.

Furthermore, shelling at the time of landing is very effective, since casualties are inflicted not only by shell fragments but by the shell-scarred areas which cause sprains and broken bones.

We also should make every effort to capture dropped equipment and supplies before the parachutists can reach them.

Hostile forces sometimes try to make a display of force by dropping dummy men and materiel. The genuineness of these must be determined at once.

c. Against Air-landing Troops

At present the enemy [United Nations] lands from 10 to 20 riflemen per glider or plane. It is necessary to annihilate these groups individually just after they land and before they can effect a concentration. Heavy fire by artillery and machine-gun units and crushing assaults by tanks are especially effective.