INTERROGATION NAV NO. 74
USSBS NO. 371

ANTI-SUBMARINE WARFARE

TOKYO 12 NOVEMBER 1943

Interrogation of: Captain KAMIDE, S., IJN; Commanding Officer of the 901 Air Flotilla from September 1943 to December 1944, and Senior Staff Member of this Flotilla from December 1944 until the end of the war.

Interrogated by: Commander T. H. MOORER, U.S.N.

SUMMARY

This interrogation covers general information on the Japanese anti-submarine effort so far as aircraft were concerned. The 901 Air Flotilla, equipped with a mixture of obsolescent aircraft made a weak effort to protect Japanese shipping against submarine attack. Organization, equipment, search and attack doctrine, development and research, and training are discussed very briefly.

TRANSCRIPT

Q. When did the Japanese organize an air fleet to be used chiefly for anti-submarine missions?
A. In December 1943 the 901st Air Flotilla was organized at TATEYAMA solely for the purpose of escorting convoys.

Q. Describe the organization of the 901st Air Flotilla?
A. When organized in December 1943, the 901st Air Flotilla was composed of one unit equipped with 48 land-based twin-engine bombers and another unit equipped with 32 four-engine flying boats. As the American submarine threat increased, the fleet was gradually enlarged. In January 1945 it reached maximum strength. The aircraft assigned were as follows:

80VOS (DAVE)
30VB (KATE)
30VF (ZEKE)
20VB(2) (BETTY)
8VPB (EMILY)

The above aircraft were moved from base to base according to operational requirements.

Q. Was anti-submarine warfare, as conducted by aircraft, given a low priority by the high command, thus making it difficult to build up the forces to the necessary strength?
A. In the beginning of the war it was not considered of great importance, which accounts for the low strength of the 901st Air Flotilla. In December 1943, prompted by serious shipping losses, we quickly increased its strength and enlarged the organization.

Q. Were all the aircraft in the 901st Flotilla land-based?
A. Yes, but the Escort Fleet also operated escorts carriers for protection of convoys. The carriers were never sent out on offensive missions.

Q. At what time during the war do you consider that aircraft were most successful against submarines?
A. Defensively speaking, it was during May 1944, at which time we convoyed ships from the EMPIRE to SAIPAN, with the loss of only one ship. Speaking from offensive standpoint, the most successful period of operation was the fall of 1944 when we were shipping very heavily between FORMOSA and the PHILIPPINES to supply the Army based there. I estimate that the Americans had over 10 submarines operating in that region and I think the flying boats were able to sink four or five of them. I lay much credit to the fact that we equipped the aircraft with MAD. No ships were lost to submarines at that time.

Q. Make an estimate of the total number of submarines sunk by Japanese aircraft during the entire war?
A. The 901st Air Flotilla estimated that they sunk about 20 during the entire war. I've no accurate information on the total number of sinkings, although they reported at one time to have sunk as high as 500. This exaggeration is caused by the fact that pilot reports are inaccurate since they are not required to furnish proof.

Q. Were the, aircraft listed in the organization moved from base to base according to the estimated location of American submarines, or according to the volume of sea born traffic in the subject area?
A. Both factors were taken into consideration when moving aircraft. Attention was given to the value of the convoy as well as the size.

309

Q. Why was this force organized in the number indicated?
A. The 901st Air Flotilla was organized with what aircraft were available, regardless of their adaptability to antisubmarine warfare.

Q. What type of aircraft was considered most effective against submarines?
A. BETTYS and flying boats. Due to the range and endurance and experience of the pilots, the above aircraft were the only type used for night operations.

Q. Did the Japanese construct a special aircraft to be used against submarines?
A. In May 1945 we developed a special plane (LORNA) for escorting convoys, which was very similar to the BETTY. Twenty of these aircraft were delivered in July 1945 and used until the end of the war.

Q. Aside from standard equipment, what special equipment was installed in your anti-submarine planes?
A. Radar and MAD; no other special equipment was carried.

Q. Was any special equipment provided for aircraft employed at night?
A. No special night equipment was used; aircraft homed on the submarine with radar until within 500 meters at which time they completed their run by dead reckoning.

Q. Did you have a special base or establishment where you studied anti-submarine warfare in order to develop special weapons for use against submarines?
A. All research was done along with other aircraft development at YOKOSUKA.

Q. What do you consider to be the outstanding anti-submarine development made by the Japanese during the war?
A. The MAD and Radar equipment.

Q. After the special equipment was developed, was it installed in the aircraft at your outlying bases or did you have to make the installations in JAPAN proper?
A. They all were originally installed in JAPAN. Toward the end of the war it was possible to make installation at outlying bases.

Q. Were the radar and MAD equipment improved as the war progressed?
A. Yes, both were improved technically as well as operationally. As a result of this improvement the range of the MAD was increased from 130 to 280 meters.

Q. Describe the depth bomb used by Japanese aircraft.
A. We had two types: 250 kg. and 60 kg. which were ordinary bombs fitted with special nose and tail adapters. The fuses employed were time fuses rather than hydrostatic fuses and were set at 3, 5, 10 and 16 seconds which gave an explosive depth of 10 meters, 45 and 80 meters respectively.

Q. Under what conditions were the above fuses used?
A. At night, when it was generally considered that the submarine would be on the surface, the 10 and 45 meters were carried. In the day time, when the submarine would spot the aircraft and thus have time to dive to a greater depth, the 45 and 80 meter fuses were used.

Q. Were any other weapons such as torpedoes used against submarines?
A. In February and March 1944 we tried to use torpedoes against submarines but after four or five months of unsuccessful attacks the idea was abandoned. The torpedo employed traveled in a reducing spiral. An attempt was made to drop the torpedo 200 meters in advance of the submarine normal to its course. It made four complete circles during which time it sank to a depth of 200 meters. This torpedo was fitted with contact fuses.

Q. Did the Japanese patrol critical areas day and night?
A. Yes.

Q. What type of search was used?
A. Sector, box and spiral searches were used depending on the situation. Sector searches were conducted at a range of 250 miles by multi-engine aircraft and 120 miles by single-engine aircraft.

Q. By what method did the Japanese maintain a plot of the position of American submarines?
A. All plots of submarine positions were kept by the Grand Escort Fleet in TOKYO. This plot included the entire PACIFIC Ocean Area. However, area commands were only furnished information concerning their own area and this was done only when special intelligence was available to the Grand Escort Fleet.

Q. Were you able to make use of RDF in order to plot the position of American submarines?
A. RDF searches were sometimes used to maintain a general plot but due to communication difficulty between various stations, the information was not received in time to be of immediate operational value.

310

Q. How did you cover a convoy with aircraft not equipped with MAD?
A. Two planes were normally used. One aircraft was continuously circling at the radius of 3,000 meters while the second plane covered the sector about 60 on each bow ahead to a distance of 5,000 meters. The angle varied with the speed.

Q. What reports were made after contacting a submarine?
A. The doctrine was to attack first, report the contact, then mark the location of the submarine.

Q. At what altitude did the aircraft normally patrol?
A. Day time, between five or seven hundred meters; at night, between two or three hundred meters.

Q. What altitude was flown when using radar?
A. The same altitude as given above was used when operating radar.

Q. Was the radar operated at all times during the patrol?
A. Continuous use at night time; shut off during the day time.

Q. Why was it not used during the day time?
A. Because the Japanese radar was not so efficient and the use of visual search was more reliable. When the visibility was bad we used radar.

Q. Did the Japanese give any consideration to the fact that the use of air-borne radar might possibly warn the submarine of the presence of Japanese aircraft?
A. No consideration was given to that fact.

Q. What was the normal range at which you expected to pick up a submarine with radar?
A. About 12 miles. Large targets were normally picked up at a greater distance.

Q. After the submarine is picked up by the radar, is the pilot able to fly directly to the submarine?
A. Yes, they can.

Q. When homing to a submarine, do you fly a collision course or fly in a curve such that the aircraft is always headed towards the submarine?
A. We fly a pursuit curve since it is necessary to keep the submarine directly ahead.

Q. At what distance does the submarine fade away from the radar?
A. The target fades at 500 meters.

Q. Did you consider the aircraft as an attack weapon, or merely as a means to discover the presence of the submarine which would later be destroyed by surface craft?
A. The aircraft was considered a primary means of destroying submarines but surface vessels cooperated whenever possible.

Q. Describe briefly your attack doctrine.
A. It was our policy to attack immediately as soon as the submarine was sighted. The submarine was not strafed since we had no guns. One or two bombs were dropped depending on the decision of the pilots. The pilots were allowed to attack at any time they thought they had a chance to damage the submarine. After making the attack, the pilot immediately made a contact report and marked the best known position of the submarine and remained on station until relieved or fuel exhausted. We had no plans of coordinated attack by more than one aircraft.

Q. Did your pilots make a special effort to avoid AA fire when approaching a submarine?
A. No, in almost every case the submarine submerged before the aircraft was in range.

Q. Did you have a plan for coordination with surface vessels during a submarine contact?
A. An effort was made to work out a plan but due to communication difficulty no cooperation was possible. The aircraft merely marked the spot and visually directed the surface craft to the scene of the contact.

Q. How long was a submarine contact followed before you abandoned it?
A. Two or three days. In planning the search during this time, it was thought that the American submarine made 3 knots submerged.

Q. Where were pilots trained to use special equipment such as MAD and radar?
A. Training was done at SAIKI and YOKOSUKA. Experienced pilots from squadrons in outlying bases were sent to the above places and thoroughly trained in the use of the new equipment in order that they might return to their squadron and train all hands. These pilots were also given special bombing training on a tame submarine at MAIZURU.

311

Q. Was any information relative to anti-submarine warfare obtained from the Germans?
A. None of value.

Q. Were the pilots assigned to anti-submarine units considered inferior to those assigned to standard combat units?
A. The inexperienced pilots, that is new pilots, were equal to those furnished to other units as replacements. An effort was made to "freeze" anti-submarine pilots but it was difficult during the last year of war because some of the best pilots were assigned to the special attack units.

Q. Did the Army ever assist in convoy duty?
A. The Army did escort work in the area assigned them by headquarters from TOKYO. There were no joint escort operations between the Army and the Navy. The Army escorted convoys at distant bases such as NEW GUINEA.

Q. What was the greatest cause of loss of the Japanese anti-submarine aircraft?
A. American fighters.

312

Table of Contents


Transcribed and formatted for HTML by Charles Hall, HyperWar Foundation