This was Japanese attack on Dutch Harbor in the Aleutian islands group at the same time as the larger 'Mi' (ii) operation against Midway island and as the precursor of 'Aob' and 'Aq' (3/7 June 1942).
Located on Unalaska island, Dutch Harbor was in 1941 the largest settlement of the Aleutian islands group. Unalaska itself is a large irregularly shaped mountainous island some 67 miles (108 km) long. Although a naval station had first been established at Dutch Harbor in 1903, the development of the more ambitious Fort Mears began only in 1940, and the port possessed only rudimentary facilities late in 1941. By as time early in 1942 there were at least four 187,500-US gal (709765-litre) fuel storage tanks, and fuel storage capacity had grown to 7.3 million US gal (27.5 million litres) by May 1943. Unalaska has so little level ground that the construction of an airstrip was considered impractical, so work of the creation of an airstrip had been started on Umnak island, just to the west of Unalaska, which has some flat terrain, but in the absence of a good anchorage all supplies had to be transported by lighter from a cove on nearby Unalaska.
After securing base areas of strategic importance in China during the course of the early stages of the 2nd Sino-Japanese War (1937/45), Japan had by 1940 decided to embark on the establishment of a resources-rich empire not only in China, Korea and Manchuria, but also farther to the south on the mainland of South-East Asia and in the major island groups lying off it, thereby creating what they named the 'Greater East Asia Co-Prosperity Sphere'. Starting with its 'Ai' attack on the US forces on Oahu island in the Hawaiian islands on 7 December 1941, which temporarily neutralised Admiral Husband E. Kimmel’s (from 17 December Admiral Chester W. Nimitz’s) Pacific Fleet, the Japanese high command rapidly followed with invasions of the Philippine islands group in 'M' (i), Malaya in 'E' (i), and the Netherlands East Indies in 'B' (ii), 'H' (i) and 'L' (i), and started work on the creation of plans for new bases from which to strike at Australia and India. By June 1942 Japanese domination of the Asian mainland had extended beyond Malaya into Thailand and Burma. In the western Pacific, it encompassed most of the larger islands in the area to the north of Australia and to the west of Midway island.
In the wake of such astounding military success, Japan decided to push onward rather than consolidate its gains, and its next objectives were therefore New Guinea in 'R' and 'Sr', and the Solomon islands group in preparation for the anticipated 'Fs' against the Fiji, New Caledonia and Samoa island groups. Between those objectives and the Australian continent was the Coral Sea, where early in May 1942 US naval forces checked the Japanese in a battle which frustrated the Japanese 'Mo' plan to establish a base area on the south coast of Papua for attacks on Australia and as a linchpin of the great defensive perimeter it was establishing with the aid of major air and sea bases on strategic island groups in the South and Central Pacific.
Remaining on the defensive throughout the Pacific, the USA hurriedly established garrisons in island bases along a great arc extending from Pearl Harbor to Sydney in Australia to keep open the shipping routes to New Zealand and Australia. With only limited numbers of troops available, the USA nevertheless joined Australia in planning an offensive in New Guinea and the Solomon islands group to halt any further Japanese advance. For overall command of this offensive, in what became known as the South-West Pacific Area, President Franklin D. Roosevelt selected General Douglas MacArthur, allocating command of the Pacific Ocean Areas to Nimitz. Thus, in addition to commanding the Pacific Fleet, Nimitz controlled US operations in three combat areas (North, Central and South Pacific Ocean Areas). Of these, the North Pacific Area extended from the western seaboard of the continental USA, Canada and Alaska westward across the Pacific to the Asian mainland. Included within this North Pacific Area were Japan’s northernmost islands, the Kurile islands group and the southern half of Sakhalin island, and just 650 miles (1045 km) to the east of these the bleak Aleutian island chain belonging to Alaska and extending in a long curve for more than 1,000 miles (1600 km) to the south-west from the tip of the Alaskan peninsula. The Aleutian islands group provided a natural avenue of approach between Japan and the USA in either direction, although the region’s generally adverse weather and desolate terrain made this approach difficult in purely military terms.
Though not characterised by the same extremes of the Arctic climate as the Alaskan mainland to their north-east, the Aleutian islands in general, and those at the chain’s western end in particular, are subject to icy winds and are often shrouded by thick fog. All of the islands are characterised by very sparse vegetation and difficult mountains. Even so, the Americans and Japanese would have been foolish to assume that their opponents would spurn the islands as an invasion route in either direction.
Japanese concern about its defence of the northern Pacific increased when 16 North American B-25 Mitchell twin-engined bombers of the USAAF lifted off the fleet carrier Hornet and bombed Tokyo on 18 April 1942 in 'Conceal'. Not knowing how the Americans had been able to undertake this raid with land-based bombers, but suspecting that it could have been launched from a secret base in the western end of the Aleutian islands group, the Japanese began to take an interest in seizing the island chain.
The Aleutian islands group first appeared as a Japanese objective in a plan prepared under the direction of Admiral Isoroku Yamamoto, commander-in-chief of the Combined Fleet. With the aid of the Imperial Japanese army, Yamamoto schemed a plan to seize strategic points in the western end of the Aleutian islands group as well as Midway island, the penultimate land mass at the north-western tip of the Hawaiian islands chain. Yamamoto saw in these two points the anchors for the defensive perimeter he envisaged in the northern and central Pacific. His plan also included in its core the final destruction of the Pacific Fleet in the 'decisive battle' at the strategic heart of Japanese naval thinking. By using the invasions of the Aleutian islands group and then Midway island as bait, Yamamoto planned to lure the already weakened Pacific Fleet from Pearl Harbor and then to annihilate it before new US construction could replace the ships it had lost in 'Ai'.
Yamamoto believed that his Aleutian islands operation, which comprised 'Aob' and 'Aq' to seize Kiska and Attu islands respectively, and 'Al' to shield the two occupation forces and also to strike the US base at Dutch Harbor on Unalaska island at a time early in June 1942, would serve as a diversion to draw significant elements of the Pacific Fleet to the north in order to challenge his forces and, according to some historians, also provide Japan with a major foothold in the extreme north of the Pacific Ocean. With the departure of the US warships from Pearl Harbor, Yamamoto would then move his main fleet to seize Midway in 'Mi' (ii).
Because of the importance of Midway, resulting from the fact that the island lay within land-based bomber range of the main islands of the Hawaiian islands group, Yamamoto concluded that Nimitz would redirect his fleet from the Aleutian islands group to Midway to prevent the loss of the strategically more important smaller island. Waiting off Midway to intercept that force would be the largest concentration of naval power yet assembled by Japan. After overwhelming the Pacific Fleet, the Japanese navy would then possess undisputed control of the central and western Pacific. Yamamoto commanded a fleet of 176 warships and auxiliaries for this overly complex operation.
A portion of that force, Vice Admiral Boshiro Hosogaya’s Northern Force (otherwise the Northern Area Fleet and 5th Fleet, Main Body, including Rear Admiral Kakuji Kakuta’s 5th Fleet, 2nd Strike Force, Carrier Force) departed Ominato on the island of Hokkaido to steam via the Kurile islands group to the Aleutian islands group, while the majority of fleet converged on Midway without the additional strength that would have been conferred by the aircraft complement of the Aleutians-bound light carriers Ryujo and Junyo.
Before Japan entered World War II, its navy had gathered extensive information about the Aleutian islands group, but had no current information on recent military developments on the islands. The Japanese high command therefore assumed that the USA had made a major effort to strengthen its defences in the area, and thus expected to find in Aleutian waters several US warships, probably including one or two small aircraft carriers as well as several cruisers and destroyers. Given these assumptions, Yamamoto had provided Hosogaya with the light carriers Ryujo and Junyo, heavy cruisers Nachi, Maya and Takao, light cruisers Abukuma and Tama, seaplane tender Kimikawa Maru, and destroyers Inazuma, Ikazuchi, Akebono, Ushio, Sazanami, Shiokaze, Hatsuharu, Hatsushimo, Wakaba, Nenohi, Akatsuki and Hokaze.
Under the command of Rear Admiral Sentaro Omori was the Attu Occupation Force with the light cruiser Abukuma and destroyers Wakaba, Nenohi, Hatsuharu and Hatsushimo (21st Destroyer Division) escorting two transport vessels (one of them the auxiliary minelayer Magane Maru and the other the 8,407-ton transport Kinugasa Maru) carrying 1,000 troops, and under the command of Captain Takeji Ono was the Kiska Occupation Force with the light cruisers Kiso and Tama, auxiliary cruiser Asaka Maru, and destroyers Akatsuki, Hibiki and Hokaze (6th Destroyer Division) escorting five transport vessels (two transports and three auxiliary minesweepers) carrying 550 troops.
Hosogaya was first to launch the 'Al' air attack against Dutch Harbor from Junyo and Ryujo, which were escorted by the heavy cruisers Maya and Takao, and destroyers Akebono, Sazanami and Ushio (7th Destroyer Division), all supported by the oiler Teiyo Maru, and then follow with an amphibious attack on Adak island, 480 miles (775 km) farther to the west. After destroying the supposed (but in fact nonexistent) US base on Adak, the troops were to return to their ships and become a reserve for two additional landings: firstly 'Aob' on Kiska, 240 miles (385 km) to the west of Adak, and secondly 'Aq' on Attu, the Aleutian chain’s westernmost island, 180 miles (290 km) from Kiska.
The attack on Dutch Harbor, on Unalaska island and therefore the most easterly of the Japanese targets, was placed first in the Japanese order of priorities as the destruction of its facilities would hamper any US response to the subsequent Japanese operations farther to the west.
Because US intelligence had broken the Japanese naval code, by 21 May Nimitz had been informed of Yamamoto''s plans, including the Aleutian undertaking, the strength of Yamamoto’s and Hosogaya’s forces, and the fact that Hosogaya would start the operation on or shortly after 1 June. Nimitz decided to confront both Japanese fleets, retaining his three fleet carriers for the Midway battle while sending a third of his surface forces to the north, as Rear Admiral Robert A. Theobald’s Task Force 8, to defend Alaska. Theobald was ordered to hold Dutch Harbor at all costs and to prevent the Japanese from gaining a foothold in Alaska.
Otherwise known as the North Pacific Force, TF8 comprised the heavy cruisers Indianapolis and Louisville, the light cruisers Nashville, St Louis and Honolulu, and the destroyers Gridley, Gilmer, McCall and Humphreys, as well as Task Group 8.2 (Surface Reconnaissance Force) with one gunboat, one oiler, 14 patrol ships and five US Coast Guard cutters, TG8.4 with the destroyers Case, Talbot, Sands, Dent, Brooks, Waters, Reid, King and Kane, and TG8.5 with six 'S' class submarines.
TF8 departed Pearl Harbor on 25 May to position itself in the Alaskan Sea some 400 miles (645 km) off Kodiak island, there to wait for the arrival of Hosogaya’s fleet. In the meantime Theobald established his headquarters on Kodiak and met Major General Simon B. Buckner, heading the US Army’s Alaska Defense Command. Authority in the North Pacific Area was divided and cumbersome: upon reaching Alaska, Theobald became commander of all Allied naval and air forces, while authority over the ground forces remained with Buckner, with whom Theobald was to work in a spirit of 'mutual co-operation'. While Theobald reported directly to Nimitz, Buckner answered to the commander of the San Francisco-based Western Defense Command, Lieutenant General John L. DeWitt, who was responsible for the defence of Alaska and western Canada. Any differences between Nimitz and DeWitt in the North Pacific Area would be referred to the Joint Chiefs-of-Staff in Washington for resolution.
On 1 June the US strength in Alaska stood at 45,000 men, of whom about 13,000 were located at Cold Bay (Fort Randall) on the tip of the Alaskan peninsula and at two Aleutian bases: these latter were the naval facility at Dutch Harbor on Unalaska island, 200 miles (320 km) to the west of Cold Bay, and a recently built US Army air base (Fort Glenn) 70 miles (115 km) to the west of the naval station on Umnak island. Without air force personnel, US Army strength at those three bases totalled no more than 2,300 men, composed mainly of infantry, field and anti-aircraft artillery personnel, and a large construction engineer contingent, which had been rushed to the area to build bases.
On arrival at Kodiak, Theobald assumed operational control of Brigadier General William C. Butler’s 11th AAF, which consisted of 10 heavy and 34 medium bombers as well as 95 fighters, divided between its main base, Elmendorf Airfield outside Anchorage, and the airfields at Cold Bay and on Umnak. Theobald instructed Butler to locate the Japanese fleet reported heading toward Dutch Harbor and to attack it with his bombers, with emphasis placed on the destruction of the two Japanese aircraft carriers. Once Japanese air strength had been removed from the equation, TF8 would engage the Japanese fleet and destroy it.
On the afternoon of 2 June a naval patrol aeroplane sighted the Japanese fleet and reported its position as 800 miles (1285 km) to the south-west of Dutch Harbor. Theobald placed his entire command on full alert, but bad weather then arrived and no further sightings of the Japanese force were made on that day.
The Dutch Harbor attack force began its run toward the target area without detection on 2 June. As noted above, Dutch Harbor was in the early stages of naval and military development, and possessed a USAAF airfield, an oil tank farm holding about 25,000 barrels, and a radio station. There was also the Fort Mears army barracks with the beached barracks ship Northwestern, a hospital and a base for Consolidated PBY patrol flying boats with the seaplane tender Gillis. On 3 June the harbour held the destroyer Talbot, submarine S-27, a US Coast Guard cutter, and two army transports. At sea guarding the Aleutian islands chain was TG8 with its two heavy cruisers, three light cruisers, and four destroyers: on 5 June this force was 500 miles (805 km) to the south-south-east of the Japanese attack force.
At 02.58 on 3 June, the 2nd Strike Force was about 180 miles (290 km) to the south-west of Dutch Harbor, making its way in dense fog and generally adverse weather. From that point Ryujo launched 14 bombers escorted by three fighters, and Junyo 15 bombers escorted by 13 fighters. As a result of the poor visibility, Junyo's aircraft could not find their target and therefore returned to the carrier. Of Ryujo's aircraft, nine attack and three fighter machines suddenly spotted Dutch Harbor at 08.08. The radar of the seaplane tender Gillis had detected the approach of the aircraft, but none of the ships had been able to clear the harbour by the time of the attack. However, the US anti-aircraft fire was powerful, and the raiders also met a few Curtiss P-40 fighters sent from Fort Glenn. The Japanese aircraft reported that they had spotted two submarines and five destroyers in Makushin Bay.
By 08.30 the raid was over, leaving the tank farm in flames, the hospital and Fort Mears bombed, and several PBY flying boats destroyed in the harbour. The Japanese losses amounted to just one bomber brought down by anti-aircraft fire.
Kakuta immediately launched an attack against the five destroyers in Makushin Bay. This effort, at 09.45, comprised 14 dive-bombers, 15 torpedo bombers and 12 fighters, together with four reconnaissance aircraft. The ever-changing Aleutian weather hid Makushin Bay from the raid, however, so the aircraft returned to the carriers at 10.50. They did, however, run into more P-40 fighters, and one Mitsubishi A6M Reisen 'Zero' fighter was shot down. At 12.00, and after recovering its aircraft, the Japanese naval force turned to the south-west.
Yamamoto then ordered Kakuta to undertake a pre-invasion bombardment of Adak, but the weather was so foul that Kakuta elected to make a second attack on Dutch Harbor. (The Adak invasion was later cancelled.) Again Kakuta was able to launch in the fog, escaping detection. At 16.04 on 5 June he despatched nine dive-bombers, 11 torpedo bombers and 11 fighters. Fair weather now exposed Dutch Harbor to attack, and this allowed the completion of the Japanese destruction of the oil farm. The hospital was again hit, and Northwestern suffered severe damage.
While the raid was going on, Kakuta’s carrier force was spotted and attacked by Boeing B-17 Flying Fortress heavy and Martin B-26 Marauder medium bombers, which managed to achieve only a few near misses that inflicted no damage, and lost two of their number in the process. The Japanese aircraft then returned to their carriers, having lost only one fighter.
In all, the Japanese raid had claimed 78 US dead and 64 wounded, as well as 14 US aircraft, while the Japanese had lost eight aircraft and suffered 10 dead, an unknown number wounded and five taken prisoner.
Just as his aircraft were landing, Kakuta received a signal from Yamamoto, whose 'Mi' (ii) undertaking was in trouble, that 'Al' was 'temporarily postponed'. The force then stood by, some 600 miles (965 km) to the south-south-west of Kiska, until returning to Japanese home waters on 24 June.
Lieutenant Colonel Matsutoshi Hozumi’s infantry battalion then occupied Attu and Kiska, without meeting resistance, in 'Aq' and 'Aob' on 5 and 7 June respectively.
During the two-day fight, TF8 had remained to the south of Kodiak island, taking no part in the action, so it was not until 5 June that Theobald sent it to investigate a report of Japanese warships in the Bering Sea heading to the south in the direction of Unalaska island, which he interpreted to be a landing force intent upon seizing Dutch Harbor. In the meantime, he instructed Butler to attack the Japanese ships with all his available aircraft. Rapidly developing clouds in the area of the Japanese ships prevented Butler’s pilots from finding their targets. Six B-17 bombers, recently arrived and fitted with air-to-surface search radar, reported scoring hits on Japanese ships, but these later proved to be uninhabited islands in the Pribilof islands, well to the north of Dutch Harbor.
It is worth noting, though, that on hearing of Yamamoto’s catastrophic defeat at Midway, the Japanese high command sent two aircraft carriers from Japan to reinforce Hosogaya in the western end of the Aleutians. Having correctly anticipated Nimitz’s next move, which was the 8 June despatch of his two surviving carriers to destroy Hosogaya’s force, the Japanese high command saw an opportunity to eliminate the Pacific Fleet’s ability to undertake far-flung operations by eliminating its only surviving carriers.
When he learned of the Japanese capture of Kiska, however, Nimitz reversed his order as he was unwilling to risk the loss of the only US carriers in the Pacific to land-based aircraft from Kiska. Moreover, he was presumably informed that Hosogaya would soon have four carriers at his disposal in the North Pacific, and opted instead to retain his carriers for spearheading a major advance into the Central Pacific.
For both sides this first stage of the Aleutians campaign had been an exercise in futility. It did not distract Nimitz from Midway, and the occupation of Attu and Kiska gained Japan nothing and eventually caused the loss of valuable ships and men. For the Japanese, Kiska without Midway no longer had any value as a base for patrolling the ocean between the Aleutian and Hawaiian chains, although the Japanese occupation of Kiska and Attu did block the Americans from any possible use of the Aleutian islands as a route for launching an offensive on Japan. Originally intending to abandon the islands before winter set in, the Japanese instead decided to stay and build airfields on both islands. Although Buckner and DeWitt pressed for a northern approach to Japan along the Aleutians, the real motive for planning the 'Cottage' and 'Sandcrab' recapture of the two remote islands was mainly psychological, namely the removal of the only Japanese foothold on US soil in the western hemisphere.