Lone Sentry: Notes on Boats and Ships in Amphibious Operations (U.S. WWII Intelligence Bulletin, June 1943)

1. INTRODUCTION

The Japanese are showing an increasing tendency to use motor landing barges instead of ships for transportation within range of United Nations aircraft in the Southwest Pacific. This change of policy is probably due to heavy Japanese losses in transports and destroyers as a result of air attacks.

The substitution of motor landing barges for transports would complicate Japanese shipping problems, but it would lessen the dangers from air attacks, because: the barges are comparatively small, they can be concealed during the day beneath overhanging trees or even camouflaged on an open beach, and they can operate at night in shallow, reef-infested waters where they are comparatively safe from destroyers and PT boats.

The 4,000-ton (gross) Japanese transport, commonly used for amphibious operations, can load 4,500 long tons, transport it 300 miles, and unload it in about 4 days.

In contrast, the large-type Japanese landing barge (daihatsu) can load a maximum of 15 long tons, transport it 300 miles, and unload it in 5 days.

Therefore, for a distance of 300 miles, 375 large landing barges would be required to do the work of a 4,000-ton transport.¹ These figures, derived from a mathematical formula, should not be applied at shorter or longer distances because the relative capacity of motor landing barges decreases with distance.

The Japanese are known to have experimented extensively with the use of small boats (mostly landing barges) for the transportation of personnel and matériel, both during and after landing operations. A Japanese experiment with both large and small types of landing barges was conducted comparatively recently in tropical waters of the Southwest Pacific. Their conclusions regarding such matters as boat capacities, use of various types of weapons on the boats, methods of unloading, and the provision of food and water are contained in documents, which are paraphrased below.

2. BOAT CAPACITIES

Japanese conclusions with regard to the capacity and efficiency of landing barges for transporting various types of troop units and equipment across large bodies of water are summarized below. The conclusions are based on experiments conducted over a distance of approximately 50 nautical miles. Using both their large- and small-type landing craft, the Japanese made the trip in 7 hours.

a. For Large Landing Barge (Daihatsu)

Unit Personnel Equipment

Rifle Co 50 None.

MG Co 40 3 HvMG.

Inf Bn gun unit 40 2 70-mm How (1 in bow ready for firing; 1 dismantled in stern).

Inf Regt Arty unit 35 1 75-mm gun.

Mt Arty unit 35 1 75-mm gun.

Rapid-fire gun unit 28 2 37-mm guns.

L Armd-c unit 15 1 L Armd-c.

[Comment: In the loadings shown above, consideration was given to the comfort of occupants, facilities for cooking, and defensive use of weapons. For landing operations where distances are fairly short, these barges could carry considerably more tonnage—probably twice as much in the case of rifle and machine-gun companies. When the large barge is used as a command boat, the Japanese recommend that 25 to 30 men make up the load.]

b. For Small Landing Barge (Shohatsu)

     Unit     Personnel       Guns

Rifle Co           25 None.

Rifle Co           20 1 HvMG.

[Comment: Capacities for units equipped with heavy weapons are not given, indicating that the small barge is not considered suitable for carrying troops and heavy equipment on a run of a full day.

For landing from troop transports, the above capacity figures for the small landing barge probably should be about doubled.]

3. CONVENIENCES FOR PERSONNEL

a. Except in the case of tank and armored-car units, benches for the men to sit on are absolutely necessary on long voyages. They must be thrown overboard before landing because it would be inconvenient to unload them.

b. Rifles should be placed in an arms rack. The best positions for the racks are in the stern or in both sides of the boat.

c. Lowering of the floor boards when there are no waves will provide better ventilation and lessen fatigue.

d. The bow operator gets tired quicker than others because he has no shelter; therefore, it is advisable to relieve him often.

e. Personnel in the small barges should stand up for 10- to 15-minute intervals from time to time.

f. Tents are absolutely necessary. Shelter tents are thin and very hot.

g. If possible, provide a utensil in each boat for boiling water.

h. A half canteen of water [per day] is necessary for drinking, in addition to the amount consumed with meals.

i. Coconut milk is very good for drinking.

j. The best method for carrying and preserving rice is to put it in a rice basket and add 3 or 4 pickled plums. [The plums are preserved by a salt solution.] Rice kept in this manner will not spoil for 17 hours or more. If it is carried in a rice box, without pickles, it is liable to spoil after 11 hours. In any case, rice must be cooked hard and its container must be dried thoroughly.

Rice carried in a mess kit, without pickles, will keep for 13 hours.

4. ARRANGEMENT OF WEAPONS

a. Rifle

The rifle should be rested on sandbags, which are to be prepared and placed on the sides of the boat for this purpose.

b. Light Machine Gun

Rather than have it handled by two men, the light machine gun should be rested on the sides of the boat for firing. It occupies too much space when handled by two persons, and the firing of rifles is interrupted.

c. Machine Guns

When using a rest for antiaircraft fire, the firing will be the same as under ordinary circumstances. In circumstances under which the rest is not used for antiaircraft firing, arrange the weapons as follows:

(1) When the left (or right) side of the boat and sandbags are used, remove the cotter pin of the cog and lower the cog sufficiently. Remove the barrel cover pin, swing the barrel in the opposite direction, and replace the pin. Essentials for aiming correspond to those for the light machine gun.

(2) When manpower is used [to hold the gun while firing], take down the gunshield and rest the front and rear legs of the weapon on the two sides of the boat. To fire, remove the barrel from the legs, tie ropes around the barrel, and hang it a suitable height.

d. Antitank Gun

To operate an antitank gun from a large boat, the No. 3 and No. 4 gunners will fire from a standing position. When adjusting the range sights, make no change in elevation, but change the direction slightly. Contact the boat captain beforehand and have the boat proceed toward the target. Depending upon the action of a moving target, set the sights at the bottom or top center, and pull the trigger when the boat is at the crest of a wave.

e. Mountain Gun

In making arrangements for firing this gun from a large boat, pile three square pieces of timber at the 10th rib to make a brace for the legs and the trail spades; put two sandbags on each of the trail spades, one bag under each wheel, and two bags on each wheel in order to prevent the gun from jumping up. At the same time, tie the wheels to the rings on the sides of the boat with ropes.

In operating the mountain gun from the boat, show the target clearly to the boat captain and have the boat advance straight toward the target. In other particulars, operate according to the essentials of direct fire. However, when the waves have a disturbing effect, fire when at the crest of a wave.

5. NOTES ON UNLOADING

Japanese instructions dealing with the unloading of troops and matériel from ships at a New Guinea port and on Guadalcanal are contained in enemy documents which are paraphrased below.

a. New Guinea

The order of unloading is mainly as follows:

(1) Land duty personnel [including unloading detail], and their necessary equipment;

(2) Antiaircraft guns (with ammunition), motor vehicles, heavy matériel (including artillery), and the personnel who operate them;

(3) Supplies, including medical stores, important articles for all units, and the necessary handling personnel;

(4) Matériel of units and the necessary handling personnel;

(5) Personnel assigned to ship duties during the unloading.

In regard to munitions ships, fuel should be removed from them first, and as fast as possible, in order to lessen the danger of fire.

Endeavor to keep intact the organization of small units, and progressively increase the unloading and transport details (particularly the latter) as the troops land.

In the past, personnel in a number of instances have hurriedly disembarked from transports to evade aerial bombing. This seriously reduced the number of duty personnel on board the ships—in some extreme cases, no one was left on board to direct operations. The result has been not only a serious delay in unloading but actually a failure in some cases to unload anything. Such occurrences must be avoided in the future and every effort put forward to unload everything down to the last articles, in spite of all difficulties.

The following paragraph on "Supplies" was included in the Japanese document:

During the unloading operations, the number of evening meals and snacks will be increased in accordance with the progress of operations. The water supply will be on the same basis. This will have a beneficial effect upon the progress of the work.

b. Guadalcanal

The order of unloading was practically the same as that given for the New Guinea port. Infantry units were unloaded ahead of the land duty personnel.

The "commander of the Guadalcanal Island unloading unit" was responsible for regulations governing the beach where the unloading took place.

(1) Use of Lights.—"Dangerous spots near the landing beach and dangerous reefs in the sea will be marked ... with faint red lights just before the convoy comes in to anchor," the document stated. Other references to use of lights were as follows:

Strict control of lights will be enforced at night. Dim lights, utilized in such a way that they cannot be seen from the air or from the sea, may be used for the following purposes:

(a) For loading or unloading ships' holds;

(b) For the inspection or repair of engines on the boats; and

(2) Rescue and Medical Care.—Each company will prepare one rescue boat, and will be responsible for rescue work between the anchorage and the shore.

During the daytime, the rescue boats will be identified by displaying a Red Cross flag.

Those requiring rescue will make circular motions with their red light at night, and will wave their red flag horizontally in the daytime.

6. HOW TO DODGE PLANES

Of particular interest to air forces are two Japanese documents which describe evasive tactics of their ships during air attacks. These documents are paraphrased below.

In cases where the planes are sighted at least 4 sea miles away, turn toward the oncoming enemy immediately and increase your speed. When the planes are about to drop their bombs, change course at a large angle (full helm). When the wind is fairly strong, change your course so as to receive a full cross wind.

When attacking planes are sighted close at hand (less than 4 sea miles), or when attacks are continuous, immediately carry out a large dodging movement. Subsequently, make continued large turns individually, without maintaining a set course. Strive to gain the benefits of cross winds as outlined above.

If you are in formation, break it and scatter according to circumstances.

¹ According to a Japanese document, the large-type landing barge is 49 feet long, 11 feet wide, and has a capacity for 10 horses, or a tank and an automobile. The speed of the boat is about 8 knots. The crew numbers seven.