"[6] The Japanese reasoned that their control of the Aleutians would prevent a possible joining of forces by the Americans and the Soviets and future attack on Japan proper via the Kuril Islands.

[7]: 19  Similarly, the US feared that the islands could be used as bases from which to launch air raids on West Coast cities such as Anchorage, Seattle, San Francisco, or Los Angeles.

On 15 August 1943 an invasion force landed on Kiska in the wake of a sustained three-week barrage, only to discover that the Japanese had withdrawn from the island on 29 July.

[12]: 47 As of 1 June, the US military strength in Alaska stood at 45,000 men, with about 13,000 at Cold Bay (Fort Randall) on the tip of the Alaska Peninsula and at two Aleutian bases: Dutch Harbor on Unalaska Island, 200 miles (320 km) west of Cold Bay, and the recently built Fort Glenn Army Air Base on the island of Umnak 70 miles (110 km) west of Dutch Harbor.

Task Force 8 consisted of five cruisers, thirteen destroyers, three tankers, six submarines, as well as naval aviation elements of Fleet Air Wing Four.

On the afternoon of 2 June, a naval patrol plane spotted the approaching Japanese fleet, reporting its location as 800 nautical miles (1,500 km; 920 mi) southwest of Dutch Harbor.

Before the attack on Dutch Harbor, the Army's 4th Infantry Regiment, under command of Colonel Percy E. LeStourgeon, was established at Fort Richardson.

Making use of weather cover, the Japanese made a two-day aerial bombing of continental North America for the first time in history.

As the Japanese pilots looked for targets to engage, they came under intense anti-aircraft fire and soon found themselves confronted by Eleventh Air Force fighters sent from Fort Glenn.

Startled by the American response, the Japanese quickly released their bombs, made a cursory strafing run, and left to return to their carriers.

When the attack ended that afternoon, Dutch Harbor oil storage tanks were burning, the hospital was partly demolished, and a beached barracks ship was damaged.

Japan installed a radar warning system on the islands and continued to resupply them, despite heavy disruptions against its shipping by US bombers and submarines.

Lieutenant Paul Bishop of the 28th Bombardment Group recalled: General Simon B. Buckner Jr. [of the Alaska Defense Command] said to us that the Japanese would have the opportunity to set up airbases in the Aleutians, making coastal cities like Anchorage, Seattle, and San Francisco vulnerable within range to attack by their bombers.

We knew that they bombed China relentlessly and by surprise on Pearl Harbor, so we had to make sure it wouldn't happen here in the continental U.S. similar to what the Germans did over London and Coventry.

Their targets included radar installations, parked aircraft, anti-aircraft artillery positions, railway, submarine base, and moored vessels.

The bombings further reduced Japan's ability to supply its bases, hampered its construction of landing strips on Attu and Kiska, and facilitated the recapture of those two islands later that year.

In April 1943 Japanese surface convoys made their final attempt to break through American naval blockade and resupply troops on Attu and Kiska but were forced to abort after being defeated in battle.

Ten days later, Grunion was attacked by three Japanese submarine chasers in Kiska Harbor, with two of the patrol craft sunk and one other damaged.

On 12 May 1943 the Japanese submarine I-31 was sunk in a surface action with the destroyer Edwards 5 mi (4.3 nmi; 8.0 km) northeast of Chichagof Harbor.

[7]: 32 A cruiser and destroyer force under Rear Admiral Charles "Soc" McMorris was assigned to eliminate the Japanese supply convoys.

[7]: 30  A shortage of landing craft, unsuitable beaches, and equipment that failed to operate in the appalling weather made it difficult however for the Americans to exert force against the Japanese.

Recorded as one of the largest banzai charges of the Pacific campaign, Yamasaki penetrated so deep into US lines that Japanese soldiers encountered rear-echelon units of the Americans.

[20] With its loss of Attu to U.S. forces, Japan was deprived of its only remaining airstrip in the Aleutians, a disadvantage that it could not compensate for because Japanese aviation units were entirely ground-based.

[7]: 33  The day before the withdrawal, the US Navy fought an inconclusive and possibly meaningless Battle of the Pips 80 mi (70 nmi; 130 km) to the west.

The allied invasion forces encountered no opposition on 15 August,[7]: 33  but their total casualties would in the end number 313 due to friendly fire, vehicle accidents, Japanese booby traps and explosives, disease and frostbite.

[23] The loyal courage, vigorous energy and determined fortitude of our armed forces in Alaska—on land, in the air and on the water—have turned back the tide of Japanese invasion, ejected the enemy from our shores and made a fortress of our last frontier.

After the war, the tundra began to take back the cemeteries and so in 1946, all American remains were relocated as directed by the soldier's family or to Fort Richardson near Anchorage, Alaska.

The shipwrecked SS Northwestern, badly damaged during the attack on Dutch Harbor, is listed on the National Register, as is a crash-landed B-24D Liberator on Atka Island.

The 2006 documentary film Red White Black & Blue features two veterans of the Attu Island campaign, Bill Jones and Andy Petrus.