The older Anglophone historiography on the invasion of the Aleutians stressed that their occupation was a diversion to lure the Pacific fleet away from the approaching Midway force. Japanese-language materials though such as the Defense Ministry's official history of the war, Senshi Sōsho, have shown that Operation AL was its own operation intended to expand the Japanese defense perimeter. The timing of the operations alone with the bombing of Dutch Harbor coming within 24 hours of Midway's bombing suggests that the IJN was not thinking of the AL as a diversionary operation as it would have given no time for the Pacific fleet to react. Yamamoto's staff conceived of AL as a package deal with Midway that would expand Japan's defensive perimeter and secure the extreme northern flank of the Greater East Asia Co-prosperity Sphere.

The Japanese conceptualized the Aleutian chain as a potential staging ground for an offensive against Japan. The fear was that instead of slogging through the Central Pacific, the USN would instead take a northerly route that could directly strike against the Home Islands. Thus occupying Attu and Kiska would be proactively denying the Americans an opportunity to use the chain for an offensive. In theory, an airfield on Attu would have allowed B-17s and B-24s to begin strategic bombing of Honshu in early 1942. The IJN was not alone in this line of thinking. Some USN planners for war with Japan in the 1900s and 10s did speculate on the possibility of a northern drive. The most prominent advocate of this policy was Mahan, who dismissed weather concerns with the idea that "white men thrive in the cold," and that the north would allow for a quick war. Billy Mitchell likewise predicted that Alaska was a lynchpin for American airpower as a steppingstone into East Asia. But Mahan and Mitchell were the only real prominent advocates of a northern route and most USN planning for Alaska was designed to prevent it from being seized by Japan.

The Japanese also had also two ancillary objectives for AL. Controlling the Aleutians would have allowed Japan to threaten the Lend-Lease supply line to Siberia, thus fulfilling its Axis duties while not violating its neutrality pact with the Soviets. Although a Japanese invasion of the USSR would prove to be a strategic dead letter for Japan, the IJN planners in early 1942 did not know that for sure. While the Germans may have been stalled outside of Moscow, the ability of the USSR to stay in the war was an open question at this period. The relatively soft nature of Dutch Harbor also made it a good target for Kakuta's carriers. The recently-commissioned Junyo's air group was quite new and inexperienced while Ryujo's was understrength.

The Japanese experience in the Aleutians showed that they had vastly overestimated the region's strategic value. The weather conditions were abysmal and made it hard for the garrison's minisubmarines and seaplanes to operate. The carrier air attack on Dutch Harbor achieved little of note. Abe Zenji, promoted to Junyo's AG and veteran of Pearl Harbor noted that not only was intelligence and planning sloppy for the raid, but that the weather conditions only made the attack worse. The garrisons on Attu and Kiska would fortify their positions, but found there was little for them to do. Even though Kiska had a fine harbor, it was difficult to resupply and the geographic remoteness of the Aleutians made it a poor advanced base.

Ironically, the Japanese invasion of the Aleutians fostered the very idea of using Alaska as an American operational base that they had hoped to prevent with the invasion.Taking back Alaskan territory was not only a political priority, but it also forced the USN to rethink older operational plans to use the area for a thrust against the Home Islands. The Americans poured a good deal of materials to build the infrastructure necessary to retake Attu and Kiska such as the Alcan highway and did deploy naval forces to intercept supply convoys. The losses in Midway and the ongoing commitment to the Solomons meant that the IJN did not have the resources to match the USN effort in the region. The Battle of the Komandorski Islands in March 1943 ended Japanese surface supply runs to the garrisons, thus making them more vulnerable. The invasion of Attu, which annihilated the island's garrison in May 1943 sealed the fate of Kiska's use. The IJN had responded to news of the Attu invasion by forming a strong task force consisting of Zuikaku, Shokaku, Hiyo, Junyo, Musashi, Haruna, and Kongo to attack the USN forces around Attu, but the invasion ended before this task force could sail. The IJN then decided to cut its losses and evacuate Kiska, which it did in July 1943.

The success of the evacuation as well as the abortive IJN task force demonstrates the real deficits of operating in the northern Pacific. Weather and space made it incredibly hard to react quickly to enemy advances in this theater. Even though the US had much greater local air and naval forces in the theater, the Japanese evacuation of Kiska went undetected. The victorious Americans likewise found little use for the recaptured Aleutians. American planners did envision a strategic bombing campaign against northern Japan and the Kuriles from the Aleutians. Although the USN and 11th Air Force did conduct air raids against northern Japan from mid-1943, these bombing missions were difficult, and not just because of Japanese resistance. Weather conditions caused a large number of bombers to abort and range limitations meant that there were few truly worthy targets for American air power.

Overall, the Aleutians were a strategic dead-end for both sides during the war. Japan found that its two islands were far-flung and hard to resupply outposts that did it little good. The Americans did pour resources into the region and while this did have long-term ramifications on Alaska's infrastructure, it did nothing to help the larger war against Japan. It is not actually not too much of a stretch to argue that the American efforts against the Aleutians were a waste of men and material. Japan soon found once it possessed Attu and Kiska there was very little it could do with them. The garrisons could not achieve much aside from delaying an American build-up in the Aleutians by their mere presence.

Sources

Garfield, Brian. Thousand-Mile War: World War II in Alaska and the Aleutians. Fairbanks: University of Alaska Press, 2010.

Parshall, Jonathan B., and Anthony P. Tully. Shattered Sword: The Untold Story of the Battle of Midway. Washington, DC: Potomac Books, 2007.