3-1 Command lines of the Imperial Navy in the northern region of Japan
Orders of operation were issued under the name of Emperor, but only in brief points. Details were to be directed by the Commander-in-Chief of the Navy General Staff. Based on the instructions from the Navy General Staff, the Commander-in-Chief of the Combined Fleet ordered the Commander-in-Chief of the Fifth Fleet, which was in charge of the defense of northeastern part of Japan, and he ordered the commanders of subordinate units and fleets. [6, p431-432]. However, the intention of the Combined Fleet Command often had considerable influences on the Navy General Staff after Admiral Isoroku Yamamoto took the position of Commander-in-Chief of the Combined Fleet. Here, the Aleutian Operation (AL Operation) refers to the period from the attack on Dutch Harbor to the occupation of Attu Island and Kiska Island by the Japanese military.
3-2 North Pacific Patrol by the Imperial Navy
3-2-1 Combined Fleet
The Imperial Navy was responsible for Japanese military operations in the Aleutian region. The main fleet of the Imperial Navy was the Combined Fleet. The Combined Fleet was an organization that controlled multiple fleets of the Imperial Navy (so called combined). Originally, it was not a permanent organization, but a temporary wartime one. However, following the signing of the Washington Naval Disarmament Treaty, the Combined Fleet was made permanent in 1922 in order to increase skills of the reduced fleet. At first, the Combined Fleet was consisted of the First and Second Fleets, but later the fleet was gradually expanded. For the Sino-Japanese War, the China Area Fleet was established independently from the Combined Fleet. During World War II, most of the fleets other than the China Area Fleet were generally incorporated into the Combined Fleet.
3-2-2 Fifth Fleet
With the opening of the German-Soviet war in 1941, the Soviet Union became a member of the Allied side, and despite the Soviet-Japanese Neutrality Treaty, Japan's international situation in the northern region had changed significantly. The Fifth Fleet, which would engage the battle of Aleutians after the beginning of the war, was established in Maizuru in July 1941 as a fleet that cooperated with the Imperial Army's "Kwantung Army Special Maneuvers (Kantokuen)" with the Soviet Union as a hypothetical enemy. The commander-in-chief of the Fifth Fleet was Lieut. Gen. Boshiro Hosogaya, and the fleet consisted of four ships: the light cruisers, flagship "Tama" and "Kiso", and the torpedo boats "Sagi" and "Hato" [4, p40].
However, since the possibility of the Soviet-Japanese war disappeared after that, the Fifth Fleet was directed to conduct patrols of the ocean off east of Japan, defense of the Ogasawara Islands, and protect maritime traffic there [4, p42].
The Fifth Fleet was strengthened after the beginning of the war, and the special seaplane tender "Kimikawa Maru", the special cruiser "Awata Maru", "Asaka Maru", and some minesweepers and submarines were assigned [4, p62]. Special cruisers were large cargo ships armed with tentative guns. The North Pacific had a vast frontage from North-Kuril Islands to Minami-torishima, and patrols in this vast sea area with few islands had not been easy. The US Task Force (mobile units) was able to make a surprise attack on eastern Japan from the north Pacific Ocean anywhere at once. Since February 1942, the Fifth Fleet formed patrol units using fishing boats to patrol the northwestern Pacific Ocean [4, p205]. However, if the US Navy attacked from this direction, it was expected to be extremely difficult to find in advance.
In order to alleviate the difficulty of patrols in the North Pacific Ocean, the Fifth Fleet had began to advocate since the end of January 1942 that the Imperial Navy occupy the western Aleutian Islands and advance the patrol line [4, p206]. In addition, the air raid on Minami-torishima by the US Task Force in March 1942 raised concerns about the north Pacific Ocean throughout the Japanese military [4, p206]. However, it is not clear how the Navy General Staff requested the Combined Fleet Command to plan the Aleutian Operation (AL Operation) to occupy Attu and Kiska Islands [4, p206]. Although the post-war recollections by the people concerned did not agree on the circumstances, the Navy General Staff seemed to have acknowledged the necessity of AL Operation in response to the proposition of the Fifth Fleet when considering the Midway Operation.
3-3 Purposes of AL Operation
In the AL Operation, how to set the purpose of the operation appeared to have a great influence on the ways of defense and support of both islands after that, so the purposes are investigated in detail.
3-3-1 Initial purposes
Summarizing the recollections of the people concerned, the Navy General Staff had initially the following three candidates for the purpose of the AL Operation to occupy Attu Island and Kiska Island: (1) Preventing the advance of the US bomber's air base to bomb Japan, (2) Advance of the patrol line to detect the US Fleet's attack on Japan in advance, (3) Blocking US-Soviet contact [4, P207]. These objectives were not narrowed down to one, and in any case Attu and Kiska were scheduled to be occupied until the autumn. On the other hand, the Combined Fleet Command thought that the purpose was to prevent the United States from deploying large bombers in the western part of Aleutian, and to prevent the US military from advancing to the north of Japan. [4, p207].
Thus, the purposes of the Navy General Staff and the Combined Fleet Command were not so different. However, some officials considered the AL Operation to be a demonstration of the Midway Operation, and their recollections of the purposes were not always in agreement [4, p207]. As if to show that ambiguity, it was not clear whether the troops withdraw from the western Aleutian Islands before the winter or permanently secure them.
Major Hifumi Mukai, commander of the Navy Third Special Landing Forces and was in charge of commanding the landing force for the occupation of Kiska, stated that he had heard an explanation of the withdrawal in September at the meeting with the Combined Fleet Command in early April, but next when he went to the Navy General Staff, he was surprised to be given a huge list of materials for the construction of a permanent base. [7, p21]
The plan of Imperial Navy's AL Operation was consulted with the Imperial General Headquarters Army Section on April 15. The plan was that "In early June, the Navy will attack Dutch Harbor and Adak Island, occupy Kiska Island and Attu Island. The Army troops will have been stationed there before the winter, and the Navy will remain during the winter." However, the Imperial Army was reluctant to occupy the Aleutian Islands and responded to the Navy on April 16 that the Army would not dispatch troops to the AL Operation [4, p208].
3-3-2 Influences of Doolittle Raid on the AL Operation
However, the Doolittle raids on Japan from the north Pacific Ocean on April 18, 1942 had a great influence on the AL Operation. The lack of patrol ability over the ocean east of Japan became clear, and the importance of patrolling the area from the northern region emerged. The Army also acknowledged the need to set up patrol bases on the western Aleutian Islands and agreed to dispatch troops on April 21 [4, p209]. Eventually, it was determined that the Army would invade Attu Island and the Navy Special Landing Force would invade Kiska Island.
The Army established the North Sea Detachment (Hokkai Shitai) on May 5 for the AL Operation, headed by Major Matsutoshi Hozumi, and consisted of approximately 1,000 men [3, p98]. This was a army unit extracted from the 7th Division of the North Army Force (Hokubu-Gun). At the same time, the Ichiki Detachment, which would be wiped out on Guadalcanal Island later, was also established.
The North Army Force had been established in 1940 and was responsible for the defense of South Karafuto (Sakhalin) and northern Japan, and consisted mainly of the 7th and 57th Divisions [3 pages: 19]. This was a corps that opposed the Soviet Union and was not actively involved in the war against the United States at the beginning of the war. Therefore, although it was not been involved in the AL Operation, this corps would gradually become involved in the battles at the Aleutians. The North Sea Detachment came under the command of the Commander-in-Chief of the Fifth Fleet beyond the meeting point of AL Operation. Then, on June 25, after the landing operation, it became under the direct control of the Imperial General Headquarters [4, p277]. The North Sea Detachment and its successors often changed their command system with the subsequent reorganization by the Imperial Army.
Captain Seiichi Kakizaki, Deputy Commander of the Navy Third Special Landing Force, stated that the initial purpose of the AL Operation for the Navy General Staff was to advance the bases for patrol line of the Fifth Fleet and to assist the Midway operation. On the other hand, for the Combined Fleet Command, it was to prevent the Japanese air raid from the Aleutian Islands [6, p433].
These thoughts had changed by the air raids on Japan by the Doolittle bombers. He stated that after the air raid, the Navy General Staff promoted the Midway Operation and the AL Operation with the primary purpose of advancing the bases for patrol line, and the Combined Fleet Command also followed it [6, p433]. In other words, the purpose of the AL Operation is to build a patrol network in the North Pacific by establishing bases on the three islands of Midway, Attu, and Kiska, as shown in the next section, and to monitor attacks on Japan mainland by US Task Forces. At the same time, it was intended to prevent advances of US air bases.
However, the operation order stated the withdrawal in winter, and there were some inconsistencies between the purpose and the order of operation as described below. You can also understand the idea of the Japanese military that if only land troops and seaplanes were stationed on the islands, the enemy's advance in this area could be prevented.
3-3-3 Details of AL Operation
The order of operation was announced on May 5, 1942. The Great Naval Ordinance (Daikai-rei), Great Naval Instruction (Daikai-si), and Army and Navy Central Agreement on the AL Operation are as below [4, p209-211]. The purposes of the operation under the Army and Navy Central Agreement were difficult to understand, but it included not only patrols to enemy task forces but also the purpose of preventing the advance of land air bases. As written in the Army and Navy Central Agreement, the occupation term was until before the winter.
The Great Naval Ordinance No. 18, May 5, 1942.
1. Commanders-in-Chief of the Combined Fleet shall secure the western key points "AF" and "AO" with the Army.
2. Details are instructed by the Chief of the Imperial Navy General Staff.
The Great Naval Instruction No. 94, May 5, 1942.
The operations under the Great Naval Ordinance No. 18 shall comply with the Army and Navy Central Agreement on Operation "AF" and the Army and Navy Central Agreement on Operation "AO".
(Note: "AF" means Midway, and "AO" means Aleutian)
The Army and Navy Central Agreement about the operation on Aleutian Islands.
1. Purpose of the operation
To secure or destroy key points in the western part of the Aleutian Islands, and to make enemy mobility and air power advance in this area difficult.
2. Policy of the operation
To invade Kiska and Attu Islands and destroy Adak's military facilities in corporate with Army and Navy.
3. Procedure of the operation
(1) The Army and Navy troops destroy Adak's military facilities in cooperation and then were removed. Next, the Army troops invade Attu, and the Navy troops invade Kiska, and secure them until before winter.
(2) The Navy supports the invasion troops by the fleet with sufficient power. Before landing, the Navy raids Dutch Harbor area by the air units from the carriers in order to destroy the air force there.
"secure them until before winter" in the Procedure of the operation can be taken to mean withdrawing from Aleutian and not patrol in winter. However, this is not realistic because the patrol net will be punctured in winter. It was guessed that the Navy would intend to remain in winter and continue patrols, as the Navy consulted with the Army in 3.3.1.
3-4 Preparation for AL Operation
3-4-1 US military
In the United States, the Navy Intelligence Department (OP-20-G) was decrypting the Imperial Navy's D code. The D code (JN-25B) was supposed to be revised on April 1, but was delayed (after all, it was revised on May 27). As of April 1, the rate of decryption of D code by the United States was 85% [2, p24].
On April 27, a cryptanalysis unit (HYPO) located in Hawaii deciphered a Japanese communication inquiring about the air forces of Dutch Harbor and Kodiak. Around the same time, Melbourne's US-Australia Joint Navy Intelligence Department deciphered communications requesting a chart of the Gulf of Alaska by the Second Fleet in the Imperial Navy. HYPO also deciphered the Midway Operation by May 15, so the US military decided that the AL Operation was a demonstrative operation of the Midway Operation. Subsequent the AL Operation cryptanalysis identified the Dutch Harbor attack as June 3 and the Midway attack as June 4 (US time) by May 28 [2, p25].
Ernest King, Chief of Naval Operations of the United States, established the North Pacific Force on May 17 to respond the Japanese AL Operation, with Maj. Gen. Robert Theobald as its commander-in-chief. King gave Theobald command of all Army, Navy and Canadian forces in the North Pacific. General Chester Nimitz, Commander in Chief of the US Pacific Fleet, formed the Task Force Tare on May 21. The name of the fleet was named after the commander, Theobald, to keep it secret from the Japanese military [8, p3].
The Navy's forces in the Alaska region consisted of two heavy cruisers, three light cruisers, 11 destroyers, six submarines, two seaplane tenders, ten coast guard boats, 14 patrol boats, and four others. In addition, 94 fighters, 42 twin-engine bombers, and 23 PBY Catalina flying boats were deployed [8, p3].
Maj. Gen. Robert Theobald
https://en.wikipedia.org/wiki/Robert_Alfred_Theobald#/media/File:RADM_Robert_A._Theobald.jpg
The Alaskan Defense Force was expanded to approximately 45,000 by June 1, 1942 [2, p18]. The Army dispatched 6,000 troops to Dutch Harbor, Kodiak, and Sitka [2, p18]. At the same time, anti-aircraft radars (SCR-270 and SCR-271) were installed in Anchorage and Kodiak.
As mentioned earlier, the U.S. Army Air Corps secretly completed the air bases in May 1942 at Cold Bay on the Aleutian Peninsula (300 km northeast of Dutch Harbor) and Fort Glenn on Umnak Island (about 120 km southwest of Dutch Harbor) [9]. As the Japanese attack on Alaska was imminent, the Fort Glenn air base was rushed by engineers to lay 80,000 iron plates to construct a runway. [9]
The aircrafts deployed around Alaska were 94 fighters, 7 four-engine bombers, and 42 twin-engine bombers. Among them were the first twin-engine P-38 fighters, radar-equipped LB-30s (British-provided B-24 bombers) and B-17 bombers. [2, P19]. The Joint Chiefs of Staff had placed the Alaskan Defense Force under the control of the North Pacific Force, but the relationship between the serious North Pacific Commander Theobald and the daring Alaskan Defense Force Commander Buckner was not smooth, which became the sources of subsequent frictions. This continued until the commander of the North Pacific Force replaced with Maj. Gen. Kincaid in January 1943.
3-4-2 Japanese military
The Imperial Navy estimated that there would be 24 flying boats, 10 to 20 Army aircraft, and 700 Marines in Dutch Harbor [4, p242]. They saw Dutch Harbor as the defensive key base in the Aleutian region of the US military, so it was necessary to give damages during the AL Operation. Other than Dutch Harbor, it was estimated that the US troops were building bases on Adak Island and Kiska Island, but believed that there would be no strong ground forces other than Dutch Harbor. The Japanese thought that it would be easier to invade Attu Island and Kiska Island if the military facilities on Adak Island had been destroyed [4, p241]. However, in fact, there were no military facilities on Adak Island.
Concerning air bases, the Japanese had only the information that there might be an airfield for small aircraft in Dutch Harbor [4, p239]. Therefore, on May 11, the reconnaissance of the western Aleutian Islands was conducted by a seaplane of the special seaplane tender "Kimikawa Maru". As a result, no ships were found on Adak Island and Kiska Island [4, p242]. In addition, from May 25 to June 1, submarine periscope reconnaissance was conducted on Adak Island, Umnak Island, and Dutch Harbor. Also, the reconnaissance by seaplanes on board the submarines "I-9" and "I-25" were conducted on Kodiak, Kiska Island, and Amchitka Island [4, p243]. The reconnaissance confirmed ships moored at Kodiak and Dutch Harbor, but no ships or facilities were found in Adak Island [4, p244]. (Please note time and date are Japan Standard Time hereafter.)
If the Japanese had conducted the flight reconnaissance on Umnak Island instead of periscope reconnaissance, they might have discovered Fort Glenn air base. Both the new Fort Glen and Cold Bay airbases would play major roles in intercepting the Dutch Harbor air raids and the subsequent air raids on Kiska Island. If the Japanese had been aware of the existence of these eastern Aleutian airbases in advance, the AL Operation might have changed the target of the Dutch Harbor attack and invaded more eastern islands to fortify.
3-5 The beginning of AL Operation
3-5-1 The attack plan of Imperial Navy
The AL Operation was to begin one day earlier than the Midway Operation. The composition of the Northern Unit responsible for the AL Operations is as follows [7, p16]. The Northern Unit was the military force temporarily organized to suit the operation, and here it was the unit mainly consisted of the Fifth Fleet.
- Main body (Commander-in-Chief Boshiro Lieut. Gen. Hosogaya): Heavy Cruiser "Nachi", Destroyer "Wakaba", "Hatsuharu".
- Second Task Force (Major General Kakuji Kakuta): Aircraft carriers "Jun-You", "Ryujo", heavy cruisers "Takao", "Maya", three destroyers, tanker "Teiyou Maru".
- Attu invasion unit (commander Colonel Takeji Ohno): Light cruiser "Abukuma", destroyers "Hatsushimo", "Nenohi", special gunship "Magane Maru", transport ship "Kinugasa Maru".
- Kiska invasion unit (commander Major General Sentaro Omori): Light cruisers "Kiso", "Tama", destroyers "Ikadzuchi", "Inadzuma", "Hibiki", "Akatsuki", "Hokaze", special cruiser "Asaka Maru", three submarine chasers, transport ships "Hakusan Maru", "Kumakawa Maru", Tanker "Kaihomaru", special cruiser "Awatamaru".
- Seaplane unit (Commander Colonel Shuichi Ushuku): Seaplane tender "Kimikawa Maru", destroyer "Shiokaze" (support of Attu invasion unit).
- Submarine unit (commander Major General Shigeaki Yamazaki): Submarines "I-9", "I-15", "I-17", "I-19", "I-25", "I-26".
- Base Air Force (Commander Lieutenant Colonel Sukemitsu Ito): East Port Air Detachment (six flying boats), seaplane tender "Kouzumaru", and others.
The aircraft carrier "Jun-yo" had a displacement of 27,500 tons and has 48 aircraft, but it was a modified version of the cargo-passenger ship "Kashihara Maru." The aircraft carrier "Ryujo" had a displacement of 10,150 tons and was equipped with 36 aircraft. They were a light class carrier and a small class carrier, respectively, in view of the number of aircraft on board. The main body of the Northern Unit departed Ominato on May 26 for the AL Operation. The fleets for the Midway Operation, including the First Task Force, departed Hashira-jima in Hiroshima on May 27 .
The actions of the Northern Unit were roughly divided into three. The Second Task Force planned to carry out air raids on Dutch Harbor and Adak Island. The Attu invasion unit was supposed to land on Adak Island, and head for Attu Island after removing there. The main body and Kiska invasion unit planned to head directly for Kiska Island [page 4: 214-215]. The three units had separate actions, but their actions were interrelated, despite the difficulty of contacting each other due to the radio silence at sea. Moreover, the AL Operation itself was related to the Midway Operation, so it was the extremely complicated operation.
Map of Aleutian Archipelago and AL operation plan
3-5-2 Intercept plan by the US military
The U.S. Pacific Fleet learned of the Japanese attack on Dutch Harbor by cryptanalysis, and on May 27, 1942 (US time), sent the North Pacific Fleet led by Commander-in-Chief Maj. Gen. Theobald, from Pearl Harbor to Kodiak. He was informed by the Pacific Fleet of the Japanese intention of only air raids, but he was afraid that the Japanese would land in Dutch Harbor because he did not trust the decryption. He placed nine destroyers in Makushin Bay, west of Dutch Harbor, to prevent landing [2, p24]. He then led the North Pacific Fleet to counterattack at landing, waiting to the southeast of Kodiak, nearly 1000 km away from Dutch Harbor. Also, the six submarines scattered to the area in charge.
Since June 1, The US troops had been on alert across the coast from Nome to Seattle [8, p4]. All patrol airplanes and 20 patrol boats scouted in the North Pacific and Bering Seas [10, p27]. Twelve P-40 fighters and six B-26 twin-engine bombers were deployed at Cold Bay base and six P-40 fighters and six B-26 bombers were deployed at Fort Glenn base to counterattack the Japanese. [2, p 26].
On June 3, two Japanese aircraft carriers were reported to be 640 km south of Kiska Island, and all Eleventh Air Force aircraft were assembled at Cold Bay and Fort Glenn bases. [8, p4]. Contrary to the Japanese expectation of a surprise attack, the US military had detected the Japanese attack in advance by decrypting the code and prepared the sufficient counterattacks in the direction of Dutch Harbor as well as in the direction of Midway.
3-5-3 Attacks on June 4 (June 3 on US time)
The Second Task Force, which is planning an air raid on Dutch Harbor in the AL Operation, suffered from stormy weather and fog, but thanks to it, it proceeded as planned without being tracked by the US military. At around 2300 on June 3, they launched three Zero fighters and 14 torpedo bombers (Kate) with bombs from the aircraft carrier "Ryujo" at a point about 330 km southwest of Dutch Harbor as the first attack air unit. They approached Dutch Harbor the following day, June 4, at 0040 [4, p245-246]. At about the same time, the radar of the seaplane tender "Gillis", which was moored at Dutch Harbor, caught a Japanese aircraft approaching [page 8: 4]. The immediate alert was issued and P-40 fighters at Cold Bay air base scrambled for interception. The alert did not reach Fort Glenn air base due to a radio malfunction [2, p29].
https://upload.wikimedia.org/wikipedia/commons/1/1e/Nakajima_B5N2_Kate_in_flight.jpg
The Zero fighters arriving at Dutch Harbor around 0100 shot two PBY Catalina flying boats about to take off and strafed oil tanks. One PBY Catalina was shot down during takeoff, but the other barely escaped into the clouds [2, p29]. Around the same time, four torpedo bombers dropped bombs over Dutch Harbor base, hitting barracks and warehouses, killing 25 people and injuring about the same number [8, p4]. Three torpedo bombers also dropped bombs, killing soldiers in the trenches. In addition, another torpedo bomber grabbed the radio room and destroyed the radio relay facility. The other torpedo bombers hit gazebos and trucks, killing and injuring several sailors [2, p32].
After about 30 minutes of attack, the air unit from "Ryujo" headed back for their carrier. Four of them engaged P-40 fighters west of Dutch Harbor, but all returned safely [4, p246]. The interceptors from Cold Bay were not in time for the battle as it arrived over Dutch Harbor 10 minutes after the Japanese aircraft left [2, p32].
On the other hand, the air unit consisted of 13 Zero fighters and 15 dive bombers was launched from the aircraft carrier "Jun-yo" as the first attack air unit. Of this air unit, only two Zero fighters joined the air unit from "Ryujo" and strafed military facilities, but the others of the air unit from "Jun-yo" turned back due to poor visibility by low clouds [4, p246]. As most of the attackers from "Jun-yo" turned back due to bad weather, the Second Task Force Command assessed that the first attack could not give sufficient damages to Dutch Harbor.
The air unit from "Ryujo" discovered five destroyers in Makushin Bay, west of Dutch Harbor, during the advance. Therefore, the Commander of the Second Task Force decided to carry out the second attack on the destroyers with all the remaining available aircraft [4, p246]. The air unit consisted of nine fighters and 17 torpedo bombers was launched from "Ryujo", and that of six fighters and 15 dive bombers was launched from "Jun-yo". In addition, four reconnaissance seaplanes (Dave) were launched from heavy cruisers "Takao" and "Maya" around 0600.
However, the widespread low clouds prevented the second attackers from finding the target, and all but the reconnaissance seaplanes turned back [4, p246]. Only four reconnaissance seaplanes, which are good at low-altitude attacks, descended below the clouds and were going to attack the destroyers. Two of them were engaged with P-40 fighters, one reconnaissance seaplane self-destructed and the other landed on the water by damages [4, p246]. The returning second attackers happened to pass over Fort Glenn base west of Dutch Harbor and were intercepted by two P-40 fighters [10, p29]. Both the first and second attackers were intercepted by P-40 fighters, so the commander of Second Task Force estimated that there was a US military land air base somewhere near here. [4, p246].
Meanwhile, the US military attacked the Japanese Second Task Force. Around 0500, a PBY Catalina flying boat attempted to approach the Second Task Force, but was shot down by escort fighters. The crew was rescued by the heavy cruiser "Takao" and became prisoners of war. Another PBY Catalina flying boat, which succeeded in approaching the Second Task Force, reported the position of the fleet before it was shot down. However, this location information was not received at Dutch Harbor [2, p33]. The crew was rescued by a US Navy Coast Guard boat.
After the air raids on Dutch Harbor, the Second Task Force was scheduled to air raid on Adak Island on the following June 5, and once headed for Adak Island. However, the Second Task Force Command thought that the weather near Adak Island was likely to be bad and that the insufficient attack to Dutch Harbor brought the necessary to attack again. The Second Task Force changed the plan and headed back for Dutch Harbor [4, p247]. The Staff of the Second Task Force would expect the severe counterattack of the US Force this time, but thought that the bad weather near the fleet would make bombing from above the clouds inaccurate [4, p247].
3-5-4 Attacks on June 5 (June 4 on US time)
The morning of June 5 was rainy over Dutch Harbor, but the weather was recovering. Around 0500, the PBY Catalina flying boat, which was patrolling, discovered the Second Task Force and reported its location. The PBY Catalina then attempted a torpedo attack, but abandoned it because one of the engines was hit [2, p33]. The report sent six B-26 bombers with torpedoes from Fort Glenn to attack. However, the PBY Catalina, which tried to guide the B-26 bombers by radar, was shot down by escort zero fighters over the fleet, in addition, the bombers could not find the fleet because of fog and clouds. Six B-26 bombers with torpedoes also headed for the attack from Cold Bay. The attackers found the Second Task Force, and several torpedoes launched to the carrier "Ryujo", but they were evaded. Realizing the difficulty of the torpedo attack, the commander of the bombers changed his tactics and dropped a torpedo from the air like a missile. However, the torpedo fell to the sea about 200 m past the flight deck of the "Ryujo", which fluctuated violently in the rough seas [2, p33].
Imperial Navy Carrier "Ryujo"
In the afternoon, two radar-equipped B-17 bombers discovered the Second Task Force. One B-17 bombed from an altitude of 300 m between fog but did not hit. The other was shot down by the heavy cruiser "Takao". Six B-26 bombers headed for the attack again from Fort Glenn. They struck the aircraft carriers "Ryujo" and "Jun-yo", but did not hit them. [2, p33] Like these, the counterattack of the US military was brave and fierce not only in the direction of Midway but also in the direction of Dutch Harbor.
At 1140, the aircraft carrier "Ryujo" launched six Zero fighters and nine torpedo bombers (Kate) with bombs to attack Dutch Harbor. At 1150, the aircraft carrier "Jun-yo" also launched five Zero Fighters and 11 dive bombers (Val) [4, p247]. The US Army meteorological station at Cape Fishermans on the eastern tip of Unalaska reported that three Japanese dive bombers headed to Dutch Harbor at 1237 after shooting down a PBY Catalina flying boat near Egg Island [2, p34].
Dive bombers bombed Dutch Harbor between clouds around 1300, destroying a warehouse, hangar, and four new oil tanks [8, p13]. A bomb hit the old merchant ship "Northwestern," which was moored at the harbor and used as a generator and dormitory, and the fire burned to a nearby warehouse. However, the ship's generator and dormitory functions were not lost [2, p34]. The dive bombers headed back for the aircraft carrier at 1340 (in the evening at local time) in conjunction with the Zero fighters [4, p247].
Meanwhile, torpedo bombers bombed the naval base in Dutch Harbor at 1320, one of bombs pierced the airship hangar, and another bomb hit the anti-aircraft gun position, killing two people. The bombs of five other torpedo bombers also hit the anti-aircraft gun position, killing four people [2, p34]. One Zero fighter was hit by this attack and tried to crash land on the plains of Akutan Island east of Dutch Harbor. However, the crew was killed when they were taken over by the mud in the swamp. Later, the aircraft was requisitioned by the US military almost intact, and the performance of the Zero fighter was investigated, which had great influences on the later air combat ways.
The Japanese attackers joined at 1000 m above the southwestern tip of Unalaska Island to set a formation on their way home. [11, p114] This point was very close to the Fort Glenn air base on Umnak Island and the Strait of Umnak. Zero fighters discovered the Fort Glenn air base and strafed its coastal facilities [8, p13], but eight P-40 fighters at the base intercepted and engaged the Japanese attackers in the air. Two dive bombs were shot down [8, p13], but two P-40 fighters were also lost [2, p34].
The U.S. military estimated that many Japanese attackers that had run out of fuel during their return had crashed into the sea as they received frequent radio calls to their fleet [8, p13]. In fact, two dive bombers were unable to find the fleet due to the fog in the dusk. The fleet was unable to turn on the searchlights, as it was known from the radio waves that large U.S. bombers were in the vicinity of the fleet. Two dive bombers that ran out of fuel self-destructed [11, p124].
On that day, the four aircraft carriers of the First Task Force were damaged in Midway, and the Second Task Force was ordered to join the First Task Force of Midway. The Second Task Force began southward at 1526 after containing the attackers [4, p248]. Commander Kakuji Kakuda of the Second Task Force reported the result of the attack on Dutch Harbor at 0400 on the June 6 as follows. The results were (1) destroy of a large hangar for flying boats, (2) shooting down of three flying boats, a large bomber, and 10 fighters, (3) submerging of a large transport ship, (4) burning of two oil tank facilities and military facilities. The damage was (1) loss of a fighter of the carrier "Ryujo", (2) loss of four dive bombers of the carrier "Jun-yo", (3) no damages of the carrier "Ryujo" and the heavy cruiser "Takao" by torpedo or bomb attacks by five large bombers. A large airfield was discovered in the northeastern part of Umnak Island [4, p248].
Commander of the North Pacific Army Maj. Gen. Theobald, in the fleet waiting southeast of Kodiak, was unable to take command due to a radio blockade. He returned to Kodiak on the afternoon of June 5, but the main battle had already ended. The U.S. military had prepared the large-scale patrol and counterattack postures for the Japanese AL Operation, but was unable to accurately track the location of the Japanese Second Task Force due to poor communications and the weather of clouds and fog. Therefore, it was not possible to give any damage to the Japanese Second Task Force.
The total damage to the US military was 68 dead and 64 injured by bombing. Twenty-five aircraft crew members were killed or taken prisoners. The aircraft lost were two B-26 bombers, two P-40 fighters, one B-17 bomber, one LB-30 patrol aircraft, four Catalina flying boats. Additionally, two Catalina flying boats were damaged. The damage to the Dutch Harbor facility was not significant except that the newly built oil tanks were destroyed [2, p34].
The air raid on Dutch Harbor was the expedition to the far east for the Imperial Navy, but they could obtain no remarkable results. There seems to have been no need to attack Dutch Harbor by the reconnaissance in late May which had revealed no military installations on Adak Island. However, the Imperial Navy sent two aircraft carriers with more than 80 aircraft to attack Dutch Harbor at the expense of strength against the Midway. Although the oil tanks were successfully destroyed, the North Pacific fleet bombarded Kiska Island in early August, as described later. As the result, the air raid on Dutch Harbor does not appear to have had significant impacts on the US military.
3-5-5 Revival of AL Operation (Occupation of Attu Island and Kiska Island)
The purpose of the attack on Dutch Harbor and Adak Island in the AL Operation was to build solid bases on Kiska Island and Attu Island while the US military could not counterattack by hitting Aleutian's military bases. If so, the discovery of a new air base in this area should have a significant impact on post-landing plans.
Combined Fleet Command issued a temporary postponement of the AL Operation at 1010 on June 5, after receiving the attack on the First Task Force near the Midway [4, p249]. In response, the Command of Northern Unit, unaware of the situation in Midway, proposed that the operation be carried out as planned. Then, Combined Fleet Command allowed the invasions of Attu and Kiska Islands at 1430. However, at 2355, when it was found that the First Task Force's carriers had been wiped out, Combined Fleet Command issued the postponement of the AL Operation [4, p250]. This postponement substantially meant cancellation of the AL Operation.
However, at 1130 on June 6, the following day, the Chief of Staff of the Combined Fleet contacted Tasuku Nakazawa, Chief of Staff of the Northern Unit, to ask for his opinion on the revival of the AL Operation. Nakazawa thought that occupying only the western Aleutian Islands would not be effective in advancing the patrol line due to the unsuccessful of the Midway Operation [4, p250]. However, it is said that the Chief Staff of Combined Fleet purposed not only the advance of the patrol line but also preventing the advance of the enemy air base as the reason for the consultation for the revival of the AL Operation [4, p251].
Commander-in-Chief Hosogaya of the Northern Unit proactively interpreted the intention of the Combined Fleet Command and issued the order of revival of the AL Operation at 1150 [4, p250]. The Japanese War History Series (official), Senshi Sosho "Navy Operations in the Northeastern", states that "It is clear that the invasions of western Aleutians was revived by the decision of Commanders-in-Chief of the Combined Fleet" [4, p250].
After that, at 1630, the command of Northern Unit received the confirmation order from the Navy General Staff that the AL Operation (invasions of Attu Island and Kiska Island) be carried out as much as possible [4, p251]. Therefore, the invasions of Attu Island and Kiska Island were proceeding as planned. However, the landing attack on Adak Island was canceled because there were no important military facilities on the island. The AL Operation plan that would not attack Adak Island was pre-planned as an option.
Combined Fleet Command prepared for the attack by the US Task Force during the invasion of Attu and Kiska Islands. Therefore, the Second Task Force heading for south returned to the Northern Unit. In addition, the aircraft carrier "Zuiho", the battleships "Kongou", "Haruna", "Kirishima", "Hiei" and the heavy cruisers "Tone", "Chikuma", the second submarine unit, and the special tender "Kamikawa Maru" were incorporated into the Northern Unit as reinforcement. When landing on Kiska and Attu, the Japanese speculated by the intercepting of US military communications that the US Task Force was heading for Kiska. On the June 6, Northern Unit and its reinforcements waited in the waters about 200 km south of Attu Island to intercept the US Task Force [4, p253].
(To be continued)
References are listed in "Reference" in the upper right-hand side.