Interrogation Nav 20, Commander Masatake Okumiya
OKUMIYA, Masatake, Commander, I.J.N.
OKUMIYA was experienced, intelligent and logical. His professional interest and enthusiasm were combined with accuracy, frankness and a knowledge of detail which made him an excellent source of information. He was for 14 years a commissioned officer in the regular Navy, served for the last 12 years as a naval aviator logging 2,000 hours of flight time. After 2 years service on a light cruiser and destroyer, he learned to fly. Thereafter he served in carrier air groups, on board carriers, and on carrier air staffs.
|Division Officer, YOKOSUKA Air Group||1939-1941|
|Aviation Instructor, KASUMIGAURA Air Station||1941-1942|
|Air Staff Officer, 4th and 2nd Air Flotilla||1942-1944|
|Air Staff Officer, Naval General Staff||July 1944-October 1945|
|Air Staff Officer, Ryujo||ALEUTIANS||June 1942|
|Air Operation Officer Staff, 2nd Flying Squadron||RABAUL||August 1942-February 1944|
|Air Intelligence Office, Japanese Naval Historical Research Department||TOKYO||August 1945|
INTERROGATION NAV NO. 20
USSBS NO. 97
CARRIER AIRCRAFT ATTACK ON DUTCH HARBOR
10 Oct 1945
Interrogation of: Commander OKUMIYA, Masatake, IJN, who served from March 1942 until July 1944 as Staff Officer with the Second Air Fleet.
Interrogated by: Captain J. S. RUSSELL, USN.
Allied Officer Present: Lieutenant H. L. McMASTERS, USNR.
As a flanking operation and diversion for the main Japanese attack on MIDWAY, the carrier airplanes of the Second Mobile (or Task) Force attacked DUTCH HARBOR on 4 June, TOKYO date, one day before the scheduled attack on MIDWAY. Because more than half the planes were turned back by weather, this attack was not considered a success and was therefore repeated on the late afternoon of 5 June, 1942. The schedule of the two ALEUTIAN occupation forces was changed, meanwhile, eliminating ADAK as an objective, but going ahead with the occupation of KISKA and ATTU. The Second Mobile Force stood by from 7 to 17 June and from 2 to 7 July in an area about 600 miles south of KISKA. During the first period a scheduled interception of U. S. air raids on KISKA was cancelled at the last moment due to weather. Details of carrier operations are given.
(All times and dates are those of TOKYO, zone minus nine.)
On 30 May 1942 the Japanese Second Task Force sortied from OMINATO, North HONSHU, and set
course for a point 20 miles south of ERIMO Point on the south coast of HOKKAIDO. The force was
composes as follows:
2 CV--Junyo, Ryujo (Flag of Rear Admiral KAKUDA, Kakuji, IJN., Task Force Commander*).
2 CA--Takao, Maya
3 DD--Ushio, Oboro, Akebono
1 AO--Teiyo Maru, and later Toho Maru
(*Rear Admiral KAKUDA was killed in action on TINIAN 1944)
Departing from HOKKAIDO the Task Force took a great circle route to a position approximately 230 degrees 400 miles from DUTCH HARBOR. Enroute, the Task Force fueled twice. Once on 1 June and again on 3 June. Three cruising dispositions were used; one for fair weather, one for poor visibility, and one for very poor visibility.
The fair weather disposition consisted of the CV's in column, distance 1000 meters, Ryujo guide and at head of the column. Disposed around the Ryujo were the three DD's, 1500 meters on either beam and ahead. The two CA's were 5000 meters on either beam of the Ryujo. Zig-zagging was used in fair weather.
In poor visibility the same formation as above was used except the three DD's formed column ahead of the Ryujo, distance 500; interval from rear DD to Ryujo, 2000 meters. In very poor visibility the two CA's formed astern of the Junyo, interval 2000 meters, distance 1000 meters. In thick weather, station was kept by position buoys, and maneuvering signals were given by very high frequency radio. No radar was installed at this time.
For air operations all heavy ships formed in line abreast with the two CA's outboard. One DD led the disposition at the center, 1500 meters ahead of the line of bearing of the heavy ships. The other two DD's took station astern of the two carriers to act as plane guards. Their distance from the CV's was varied with the speed of the CV's. At high speed the plane guard DD opened to 1000 meters and at slow speed closed to 700 meters.
The mission of the Japanese Second Task Force was to attack ships, planes, and shore installations at DUTCH HARBOR as a diversion to the attack on, and occupation of, MIDWAY, and then to support landing operations in the Western ALEUTIANS. (Commander OKUMIYA actually stated that the occupation of KISKA and ATTU was planned. However, in a later interview, Captain ITO, Taisuke, Fifth Fleet Staff Air Officer, who was concerned with the planning of the occupation, said that the occupation of ADAK, KISKA, and ATTU were considered, with the selection to depend on photo reconnaissance. After the Japanese reverse at MIDWAY, Admiral YAMAMOTO was greatly opposed to the occupation of any of the ALEUTIANS, but was persuaded by Vice Admiral HOSOGAYA, ComFifthFleet, to permit the occupation
of ATTU and KISKA).
The attack on DUTCH HARBOR was scheduled for 4 June (TOKYO Time), one day earlier than the carrier air attack on MIDWAY. This schedule was met.
The second Task Force's speed of advance was limited to 10 to 11 knots due to the slow speed of the accompanying AO. On 30, 31 May and 1 June, they steamed in dense fog. The existence of a mild front was known and they attempted to stay in the thick weather ahead of it.
On the morning and afternoon of 2 June and on the morning of 3 June, two 2-plane sections scouted ahead to a distance of 120 miles. On the afternoon of 3 June, four 2-plane sections scouted an area 30 degrees on either side of the Task Force track to a distance of 250 miles.
As to intelligence of American Forces, the Japanese Second Task Force had various reports from submarine reconnaissance. From a position off the WASHINGTON State coast, a submarine had launched a reconnaissance seaplane which scouted SEATTLE Harbor and reported no heavy men-of-war, particularly CV's, there. About 30 May a similar plane launched from a submarine about 100 miles north of DUTCH HARBOR scouted that port and reported only a few small merchantmen present. This plane was damaged in landing due to the swells and could not make a scheduled reconnaissance on 3 June. Instead, DUTCH HARBOR was examined by periscope with a negative report made on that date. Two other submarines were patrolling on a line south of COLD BAY; these made no sightings. A periscope reconnaissance of KODIAK was made about the end of May with a negative report. A submarine plane scouted KISKA about 25 May and reported no ships present. The submarine borne planes maintained radio silence during their flights, with orders to break radio silence only if they were chased by American planes. All reports were made by the mother submarine. The submarine off SEATTLE and the on off KODIAK maintained station for some time. The only contact reported by the KODIAK submarine was that of sighting one large merchantman on a date which Commander OKUMIYA did not remember.
During fueling on 3 June, the second Task Force heard the engine of an American plane and thought they saw a flying boat. One of 2 VF, airborne on combat air patrol, gave chase but lost contact in the poor visibility.
The following air operations were planned for the attack against DUTCH HARBOR on 4 June: The first wave was to be launched at earliest light of dawn (2330, 3 June), and the second wave one-half hour thereafter:
|Attack Seaplanes||Takao--2,||Maya--2,||Total 4|
The two 3-seat seaplanes, one each from Takao and Maya, were to scout to the eastward.
The Second Task Force had the following operational planes available prior to launching the first attack on DUTCH HARBOR:
Ryujo- 12 Type 0 VF, 18 Type 97 attack bomber VT; Junyo- 18 Type 0 VF, 18 Type 99 dive-bomber VB; Takao- 2 Type 95 two-seat reconnaissance seaplanes, 1 Type 94 three-seat reconnaissance seaplane; Maya- 2 Type 95 two-seat reconnaissance seaplanes, 1 Type 0 three-seat reconnaissance seaplane.
Weather, that is fog and low clouds, interfered considerably with the execution of the air plan. The first wave was launched on time at a point about 210 degrees, 180 miles from DUTCH HARBOR. The visibility was from 2000 to 5000 meters. One VT from the Ryujo had a forced landing in the sea immediately after take-off. The crew of the plane was rescued. As the planes of the first wave flew towards DUTCH HARBOR they ran into increasing difficulties due to weather. All of the Junyo's planes turned back, and, of the Ryujo's planes, only 6 VF and 6 VT got through to the target. The 6 VF found no U.S. fighters so strafed a Catalina flying boat on the water. The 6 VT attacked the radio station, warehouses, pier and shore installations. 2 of 3 Ryujo VF found a Catalina close to the shore and shot it down. A photo proved that this American plane crashed and burned. One of the 9 Junyo VF, after being airborne for about one hour found a Catalina and after a chase shot it down in the vicinity of the carriers. Commander OKUMIYA stated that both Catalinas burned. Another of the first wave VF found a Catalina but it got away in the clouds. One VT from Ryujo found 5 to 6 U.S. DD's in MAKUSHIN BAY. Upon receipt of this information the second wave, which had been held on deck due to weather, was launched at about 0900 4 June. All the planes of the second wave turned back except the 4 seaplanes from the cruisers. Two of these were intercepted over the U.S. DD's where one was shot down and the other damaged. One of the Ryujo's VF failed to return after announcing it was making a forced landing on AKUTAN. (It was intended that the submarine lying to the north of DUTCH HARBOR would pick up any Japanese aviators forced down; the latter had been instructed that, in the event of forced landing, they were to endeavor to land on one of the small islands off UNALASKA Island.) The final casualty of the day occurred when a 3-seat seaplane, returning to its cruiser from a scouting mission to the east, cracked up on landing. The personnel were rescued. Of the second wave of carrier planes, all of which turned back due to weather, only three saw any action. Three fighters strafed a U.S. submarine off the south coast of UNALASKA Island. After the first two VF made strafing passes the third said the submarine submerged so that he could not make an attack. During the day the Task Force had moved toward shore, so that, when the second wave planes landed, their parent carriers were only 100 miles from DUTCH HARBOR. A combat air patrol of 2 VF was maintained over the force through the day. Patrols were of 2 hours duration and were launched alternately by Ryujo and Junyo. All planes were aboard by about 1500, 4 June, at which time the Task Force began a retirement on approximately the reverse of their approach course.
Visibility continued to be poor and the Japanese weather forecast indicated that the weather at DUTCH HARBOR would probably be worse on the following day. After refueling DD's from the carriers in partial darkness beginning at about 0000, 5 June, they laid a course to the westward with the idea of making an air reconnaissance of ADAK and ATKA. At sunrise ADAK bore 300 degrees distance 250 miles; however, the wind velocity was from 25 to 30 knots and the sea high, hence no planes were launched. They continued to the westward hoping the weather would improve, but returned to their sunrise position at about 0300 or 0400. At this time the TOKYO weather report indicated that the weather might be improving at DUTCH HARBOR. They therefore headed towards that place. They sighted one or two PBYs fairly early in the morning and one about two hours later. At 0900 they launched 2 VT from Ryujo for a
weather reconnaissance of DUTCH HARBOR. These planes found 1 U.S. DD south of UNALASKA Island. They reported that the weather in the vicinity of DUTCH HARBOR was not good, but a little better than the preceding day. It was therefore decided to launch a second attack against DUTCH HARBOR. Meanwhile, various air attacks were developing against the force. The visibility was poor and the recognition of enemy planes as to type was uncertain. Commander OKUMIYA thought only PBYs and B-17s were involved. Four protective fighters were launched. They chased and shot down one PBY and believed the damaged a second one. Various planes were taken under fire by the ships of the Task Force. The TAKAO, well out on the left flank of the formation, shot down a B-17 and took one prisoner. One DD had two bombs dropped on her, but these missed by about 500 meters. One bomb hit well clear of the Junyo. Some planes, which Commander OKUMIYA thought were B-17s, but which could have been B-26s, he said, made torpedo runs although no torpedoes ran close to the ships. One plane after making a torpedo run passed diagonally over
the deck and dropped an object which he thought to be a torpedo. The object passed over the Ryujo, but struck the water about 200 meters on her port quarter and did not detonate.
Between these various attacks against them, and at about 1100, the second day's attack against DUTCH HARBOR was launched, Because of the poor weather, only the most skilled pilots were allowed to participate. Only one wave was launched. It was comprised as follows:
All planes reached the target, but reported that enroute they dodged considerable cloud masses. No U.S. fighters were encountered at the target so the Japanese VF strafed ground targets. The VB and VT bombed the aircraft hanger, oil tanks, one transport alongside a pier, and warehouses. Photographs showed a large fire which they believed to be the hanger burning.
The attack group from the Junyo had a rallying and rendezvous point the west end of UNALASKA Island. When they arrived at this rendezvous point they were attacked by about 10 U.S. fighters. In the ensuing dogfights 2 VF and 2 VB from the Junyo were shot down. It was estimated that 5 or 6 U.S. fighters were shot down. The Junyo planes reported a large U.S. flying field on the east end of UNMAK Island, the location of which was hitherto unknown to the Japanese.
The Ryujo recovered all of her planes about one hour before sunset, none were lost. Due to the delay involved in the dogfight over UNMAK Pass, the Junyo's planes were late returning and did not land aboard until sunset. Her losses were the 2 VF and 2 VB shot down by U.S. fighters over UNMAK Pass, and one VB which, during the fight, had its radio receiver knocked out and became separated from the flight. Its transmitter, however, was working, and it called in several times reporting fuel remaining and requesting navigational assistance which Junyo could not give because the plane could not receive. It is presumed that this plane went down at sea. Total losses for the day's attack were 2 VF and 3 VB, all from Junyo. No surface ship of the Second Task Force was damaged either day of attacks against DUTCH HARBOR.
After the second attack against DUTCH HARBOR on 5 June the Second Task Force retired to a point about 600 miles south of KISKA where the Zuiho, together with two ships (sister ships which Commander OKUMIYA thought may have been the Kongo and Haruna) and 4 DDs joined. The Zuiho had been with a detached group of ships at the Battle of MIDWAY and had survived that action. This augmented task force cruised between 7 and 17 June in an area south of KISKA with the object of cutting off any U.S. carrier force which might be sent up from the MIDWAY force to interfere with the Japanese landing operations on KISKA and ATTU.
No vessel from the Second Task Force went into KISKA, nor was air cover provided over KISKA by carrier planes, although an interception of U.S. planes attacking KISKA was planned and the force moved up to a point 250 miles south of KISKA for that purpose. Weather, however, prevented the launching of any fighters for the planned interception. When weather permitted, two training flights were launched daily, four planes in the morning and four in the afternoon. Air searches were also made when practicable. One of the latter extended into the BERING SEA to a distance of 100 miles north of KISKA about the time the interception was being planned.
The Second Task Force exchanged recognition signals with the seaplane carrier Kimikawa when she was enroute to KISKA. When the ship arrived in KISKA on 15 June and had discharged her seaplane fighters, seaplane fighter reconnaissance planes, their fuel and other logistic materials, the Second Task Force returned to OMINATO where they arrived on about 23 June.
They sortied again on about 30 June reinforced by the addition of the aircraft carrier Zuikaku, a survivor of the CORAL SEA action in which the Shoho was lost. (CV's now with Second Task Force were Ryujo, Junyo, Zuiho, and Zuikaku). This force patrolled south of KISKA, and a little west of their former patrol area, between the approximate
dates of 30 June and 7 July.
Miscellaneous Information from Commander Okumiya
Arming and Fuzing
For the attack against DUTCH HARBOR planes were armed as follows:
|VB||--||one 250 kg bomb, fused nose and tail, half the bombs with 0.05 sec, and half with 0.1 sec fuzes|
|VT||--||one 250 kg and four 60 kg bombs, the former with nose and tail fuses of 0.05 sec delay, the latter with nose fuzes only of 0.05 sec delay|
|Two-Seat Seaplanes||--||two 60 kg bombs, with 0.05 sec delay nose fuze only|
Weather forecasting was done in TOKYO and was excellent so far as wind and general weather were concerned, but the forecasting of fog was poor. The carrier force made use of a weather front in their approach on DUTCH HARBOR. This front did not exist at first but a low pressure area developed which was used to their advantage so far as concealment was concerned but it made scouting difficult.
Weather limitations for carrier operation:
|Max. true Surface Wind:||for Ryujo||--||15 meters per second (29 knots)|
|For Junyo||--||18 meters per second (35 knots)|
Visibility: 5000 meters, but desired better visibility in a quadrant or semi-circle of bearing from the carrier. (At the DUTCH HARBOR action the visibility went down to 1000 meters, but operations were conducted because of the importance attached to them, -- i.e. timing with MIDWAY and the occupation force.)
|Ceiling:||500 meters desired (200 meters was accepted at DUTCH HARBOR).|
|Sea:||Pitching not so important as rolling|
|Limiting Roll:||10 degrees.|
|Limiting Pitch:||5 degrees.|
Second Task Force estimated 30 large landplanes at KODIAK, some large planes at NOME, no landplanes but about 12 patrol-bomber seaplanes at DUTCH HARBOR.
They thought a small landplane field existed at DUTCH HARBOR, but had no knowledge of fields on UNMAK or on the ALASKAN peninsula. They believed, without specific intelligence, that seaplanes could base at ATKA and ADAK, and that, at both these places, terrain could be found upon which an airfield could be built. ww2dbase
Source: United States Strategic Bombing Survey (Pacific) Interrogation of Japanese Officials [OPNAV-P-03-100], courtesy of ibilio Hyperwar Project
Added By: C. Peter Chen
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Thomas Dodd, late 1945