The July/August 2021 issue of Archaeology had a great article on the field work being done out on Kiska Island in the Aleutian Islands. You can read the article here: The Cold Winds of War – Archaeology Magazine
There are plenty of good contemporary photographs of the artifacts remaining on the islands, including an anti-aircraft installation.
The article states, “Historians have frequently portrayed Japan’s invasion of the Aleutians as a feint meant to divert American attention from its real target, Midway. However, [Archaeologist Dirk H.R.] Spennemann argues that the evidence from Kiska makes clear that the Japanese invested a great deal of resources there and saw occupying the island as an important strategic goal in itself. He points to the solidity of the wooden barracks they built, which they surrounded with high barriers of sod cut from the tundra to protect against the wind and cold. By contrast, when the Americans retook the island, they camped in tents with low sod barriers. The Japanese also constructed miles of tunnels on the island to provide refuge from U.S. bombs and even installed a network of cast-iron fire hydrants in their navy camp. ‘All of this indicates a lot of effort and that they intended to stay,” Spennemann says. “You don’t put that effort in for two or three months. This is something the historic data set doesn’t tell you, but which the evidence on the ground shows you.'”
There’s also some supplementary photos they’ve put here, The WWII Battle for Alaska – Archaeology Magazine.