INTERROGATION NAV NO. 47
USSBS NO. 199

CONVOY ESCORT AND PROTECTION OF SHIPPING

Interrogation of: Rear Admiral HORIUCHI, Shigetada, IJN, Chief of Staff, First Escort Fleet from May 1944 to December 1944; Commanding 901 Air Group, FORMOSA from January 1945 to September 1945.

Interrogated by: Captain Steadman Teller, USN.

SUMMARY

Submarine attack was the greatest menace to Japanese shipping in the SOUTH CHINA SEA and adjacent waters throughout the war. Carrier-based air attacks became an important factor in September and October 1944 and caused a major change in shipping routes between the Japanese EMPIRE and N.E.I. and also forced a revision in convoy organization. Land-based air attacks became important after 1 January 1945, practically eliminating surface supply to FORMOSA and forcing abandonment of air cover to convoys by 1 April 1945.

Inefficient administration and control reduced the full employment of shipping. Lack of escort vessels also prevented its full employment.

TRANSCRIPT

Q. When you became Chief of Staff, to the First Escort Fleet in May 1944, what did you have in the Escort Fleet?
A. At the beginning the strength of ships consisted of approximately ten destroyers, eight coast defense ships, three mine sweepers, one or two chasers, and one or two armed transports. The armed transports carried very little freight and were called special gun boats. At that time the organization was called First Escort Squadron. In November 1944 the title was changed to First Escort Fleet.

Q. What was the area of responsibility of the First Escort Fleet?
A. The area included the supply line from MOJI to FORMOSA to the PHILIPPINES to SINGAPORE and North BORNEO and a line to PALAU. It did not include the MARIANAS.

Q. What other fleet, besides the First Escort Fleet, was carrying out convoy duty at that time?
A. The First Escort Fleet was the only organization responsible for convoying ships over long distances; such as, from the EMPIRE to the PHILIPPINES and EAST INDIES and PALAU. However, in each outlying area such as SINGAPORE, SOERABAJA, AMBON, MANILA and TRUK the Area Fleet of that locality was responsible for the escort duty. In the case of the MARIANAS, the Second Squadron was responsible. Escorting in the RYUKYU ISLANDS was under the control of the Commander of SASEBO Naval Station. This escort responsibility terminated at KIIRUN, FORMOSA.

Q. As your escort squadron increased in number, how did the organization change?
A. The escort ships were grouped in one, two or three ships to accompany an important convoy at first. The senior captain of the escorting vessel acted as convoy and escort commander. This however, proved too burdensome for the senior commander, and consequently about the summer of 1943, the practice was begun to assign a convoy commander with the rank of captain to each important convoy. By May 1944, there were 15 such captains assigned to the First Escort Fleet. About June 1944, further strengthening of the organization was made by adding four Rear Admirals as escort convoy commanders. These officers were placed in command of the more important convoys and commanded both the escort and the ships being convoyed. In these cases, the captains mentioned above were in charge of the convoy ships only. These groups sometimes convoyed ships to MANILA, but for the purpose of reinforcement of LEYTE, the commander of the fleet at MANILA (Southwest Area Fleet) took charge of the operation for this purpose. In July, an additional organization was set up called Coast Defense Group of which four were organized to augment convoy protection in particularly dangerous waters. These groups were composed of coast defense ships and were commanded by captains or commanders. By November 1944, the First Escort Squadron had a total of 60 vessels composed of approximately four destroyers, 45 coast defense ships, four sweepers, two subchasers and one or two special gun boats which were the converted transports. The First Escort Squadron was commanded by Vice Admiral NAKAJIMA, Torahiko, whose headquarters were at TAKAO. In

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November, the First Squadron became the First Escort Fleet and Vice Admiral KISHI, Fukuji took command. The Grand Escort Fleet Headquarters in TOKYO was responsible for escorting matters throughout all areas. The Commander of the Grand Escort Fleet issued general instructions to subordinates regarding matters of convoy, and exercised authority over Commandants of.,all Naval Stations with regard to escort matters.

Q. Did you convoy Army ships in your group?
A. Yes, the Grand Fleet Headquarters in TOKYO arranged for the make up of the convoys including Army ships which during the time of my duty, made a large proportion of the traffic. These Army transports were paced under the convoy commander and remained under his command until they arrived at their destination.

Q. Did you have adequate communications to conduct the operation of your various forces?
A. The communication between main escort fleet headquarters and outlying stations and ships en route between them was adequate. Communication to aircraft involved in convoy protection was mainly via the bases of the aircraft. Due to the limitation of equipment and training of communication personnel, the ship-to-plane communication was not very satisfactory. A training program on voice radio was undertaken and improvement was being made by January 1945.

Q. Was the full employment of ships prevented by any of the following causes and if it was, to what degree: Inadequate administration and control of shipping, lack of crews for the ships, or lack of escorts?
A. In administration, there was a certain amount of inefficiency due to the divided control of ships between the Navy, the Army and Ministry of Transport. This divided control led to inefficiency in distribution of material for repairs, of the proper assignment of facilities to effect the repair and in the distribution of crews. For example, at the point of repair the administration powers were actually under Navy control; but in the case of merchant vessels, the Ministry of Transport was responsible for initiating the repair. These deficiencies were important throughout the war. When submarines sinkings became very high, the inadequate number of escort vessels became an important factor in the reducing the usefulness of ships, as convoys would remain in port awaiting proper escorts.

Q. What was the most serious form of American attack on your ships during the time you were Chief of Staff of the Escort Fleet?
A. Throughout the war, submarines were the most important constant menace. In October 1944, Carrier Task Force attacks were most serious. The operation of land-based aircraft did not assume an important threat until about one month after I left my duty with the Chief Escort Fleet, in January 1945.

Q. What changes in your convoy procedure were caused by the carrier attack in September 1944?
A. In October 1944, as a result of the Carrier Task Force attacks along the PHILIPPINE and FORMOSA line, the convoy route to SINGAPORE was changed from the west coast of PHILIPPINES to the east coast of the ASIA Mainland. If we had intelligence of impending Task Force attacks, we would order the convoys to scatter.

Q. What effect did the Carrier Task Force attacks on SAIGON and HONGKONG have on convoy procedure?
A. Because the supply of petroleum production to JAPAN from the NETHERLAND EAST INDIES was most important, it was essential that convoys continue along the Asiatic Coast. These convoys were made smaller and the strength of the escorting vessels was greatly increased including destroyers and occasionally a cruiser. These convoys were organized for a fight until the finish.

Q. When you were commandant of the 901st Air Group at TAKAO, how many aircraft did you have for convoy protection?
A. When I took command of the First Escort Fleet Air Squadron, its authorized strength was 212. Actual strength was 170 aircraft of the following types: Flying boat -- both Type 97 and Type 2, Zero Type land-based fighters, carrier type attack planes, land attack planes -- Type One and Type 96, Zero Type seaplanes (three seats) and spotters (two seats). This air squadron was responsible for convoy coverage in the area south of Lat. 27ÉN and north of Lat. 8ÉN covering the entire SOUTH CHINA SEA and shore of PHILIPPINES and the Asiatic Coast. The most important bases for operation were in FORMOSA, TOKO (Seaplanes), BAKO (landplanes), TANSUI (seaplanes); in the PHILIPPINES, MANILA (landplanes and seaplanes), IBA (landplanes), SAN FERNANDO DEL NORTE (seaplanes), LAOAG (landplanes), and BASCO in the BATAN Islands (landplanes); on the Asiatic Mainland; AMOY (seaplanes), HONGKONG (landplanes and seaplanes); on HAINAN, SANGAH (landplanes and seaplanes). Most of my fighters were concentrated there -- HAINAN. My headquarters were at TOKO, FORMOSA.

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Q. Did you not have twin-engine bombers specially equipped for anti-submarine work?
A. We had at the most 36, Type 96 bombers, divided between FORMOSA, LUZON and HAINAN. Half with radar and half with the magnetic device, which was very effective in detecting submarines.

Q. Did the aircraft which carried this magnetic device also attack the submarines, or did it merely discover them for your surface vessels to attack?
A. Both. It delivered air attack or called other planes and surface ships in to attack. Indication of submarines was made by visual method; planes would maneuver or signals would be dropped from planes.

Q. Was your aircraft strength kept at 170, or was it increased or decreased?
A. It decreased.

Q. What was the principal cause of the decrease?
A. A steady decrease was due mainly to the continuous daily attacks from the PHILIPPINES based landplanes on bases in FORMOSA. Losses at air bases along the Asiatic Coast were suffered from attacks by planes based in CHINA.

Q. To what extent did single search planes coming from PHILIPPINES interfere with your protection?
A. The attack by single search planes from the PHILIPPINES wasn't very important. Occasionally Carrier Task Force attacks would also damage our air strength. The end of March, because of the constant air attacks, the aircraft of the First Escort Fleet Air Squadron were forced to withdraw from the South CHINA Coast and FORMOSA Coast to SHANGHAI and KYUSHU.

Q. Did the Army fighters assist you in protection of convoys along the South CHINA Coast?
A. The Army group, Number Two Air Group, stationed at CANTON, assisted on calls and sometimes by flying over convoy ships. However, there were not many, airplanes available.

Q. To what extent did American aircraft interfere with surface supply of FORMOSA?
A. By the end of January, large ships could only come to KIIRUN, and coast traffic around FORMOSA was limited to very small craft moving at night. TAKAO was completely closed to large ships.

Q. To what extent did the night aircraft interfere with shipping to TAKAO?
A. The attacks on small boats plying between the PESCADORES and FORMOSA Area at night were very severe.

Q. What were your most important missions?
A. The most important missions in my area were: first, to protect the shipping of oil from the south to the EMPIRE; second, the supplying of the PHILIPPINES. I must confess that both missions failed. It is my opinion that although the officers assigned to convoy duty fully appreciated the vital strategic importance of maintaining supply lines to keep the Combined Fleet able to operate at all, the high command took the counsel, short sighted, of the Combined Fleet Staff in allocating insufficient strength to the maintenance of the vital supply lines. Convoy officers were only specialist auxiliaries of the Main Force and became therefore important.

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Transcribed and formatted for HTML by Charles Hall, HyperWar Foundation