By mid-1944, American submarines were extending their patrols into the northern Pacific, including the Kurile Islands chain, to interdict Japanese shipping and isolate enemy garrisons. Following the Aleutian Islands campaign (1942–43), Japan’s remaining bases in the Kuriles (stretching from Hokkaido to Kamchatka) were targets for periodic U.S. air raids and naval harassment. Older S-class submarines had prowled these cold northern waters early in the war, and notably the USS S-44 was sunk off Paramushiro by a Japanese escort in October 1943. By 1944, fleet submarines from Pearl Harbor and Midway took up patrols in the area. The USS Barb (SS-220) and USS Herring (SS-233) were among the U.S. subs assigned to the Sea of Okhotsk and Kuriles, hunting convoys that supplied isolated outposts. Barb was now under the command of Commander Eugene B. “Lucky” Fluckey (who had taken command in May 1944), while Herring was on her eighth war patrol under Lieutenant Commander David Zabriskie, Jr.. These two submarines would rendezvous in late May 1944 to coordinate their efforts against Japanese shipping in the region.