Here’s what you’ll learn when you read this story:

• The World War II-era battle for the Aleutian Island of Attu claimed two shipwrecks—one from Japan and one from the United States.
• Recent explorations found and investigated those wrecks for the first time, using sonar and drones to document the underwater battlefield.
• American bombers sank the Japanese ship, while the American ship ran aground on an underwater pinnacle.

Researchers recently dipped into the Bering Sea to investigate one of the least-studied theaters of World War II. They came away with evidence of two lost ships—the Kotohira Maru from Japan and the SS Dellwood of the United States—that sank near Attu, one of Alaska’s Aleutian Islands.

Researchers used sonar, underwater drones, and historical records to locate the ships, which were lost during the buildup and aftermath of the three-week Battle of Attu in 1943. In this first systematic survey of Attu’s underwater cultural heritage—now published in the journal Heritage—researchers found that the remains of the Japanese transport ship and the American cable-layer had experienced far different fates.

The Kotohira Maru was launched in 1918 by Osaka Iron Works Ltd. The 6,101-ton vessel was a coal-powered, single-screw steam ship and general cargo carrier, and it supported the invasion of Burma (now Myanmar) before being reassigned to the Kuril Island sector (Japan’s northernmost outpost).

On Dec. 31, 1942, the Kotohira Maru headed to Attu without an escort, carrying lumber, provisions, fuel, and supplies for Japanese soldiers. (It may have also transported a platoon of troops, but that isn’t certain.) While approaching the island from the west early in the morning of January 5, 1943, the Kotohira Maru rounded Attu’s northeastern corner in search of Holtz Bay, Japan’s most heavily defended position. While doing so, it was spotted by an American pilot and subsequently bombed by American B-24 Liberators. A 500-pound explosive eventually sank the Kotohira Maru, sending it—and its final crew of 30-50 sailors, all of whom died in the attack—to depths of nearly 300 feet.

Historical reports from the American pilots gave the research team a starting point for their search, which eventually located the Kotohira Maru largely intact. The ship was sitting upright, with its recognizable hull lying near the severely damaged (and detached) bow, matching an account that indicated a direct bomb strike to the bow. Cargo hatches, a steam engine, a scotch boiler, and the ship’s distinctive counter stern were all clearly visible.

The SS Dellwood’s fate was entirely different. The ship was transferred to the U.S. Maritime Commission 10 days after Japan’s attack on Pearl Harbor, having started its life as a cable ship in 1919. In a military capacity, it ran regular trips from Seattle and the Puget Sound to northern military facilities in Alaska. The Dellwood arrived at Attu in July 1943 following the U.S.’s victory at the Battle of Attu and set to work establishing a cable between the island’s command headquarters and the newly established airfield on the island of Shemya. Unfortunately, the ship struck an uncharted, submerged pinnacle off Attu’s Alexai Point, near the entrance of Massacre Bay. Other ships came to the aid of the Dellwood, but the damage was severe, so salvage personnel stripped it of valuables before it sank.

This latest exploration discovered the Dellwood completely flattened about 115 feet below the surface, with its debris field spread across the seabed. Intentional postwar demolition—likely intended to clear the harbor for navigation—left the ship largely unrecognizable, though the distinct cable-laying machinery was intact.

“While neither Kotohira Maru nor SS Dellwood were directly involved in the Battle of Attu,” the authors wrote, “the presence of both wrecked vessels represents critical aspects of the war effort that extend beyond those three weeks in May 1943.” For instance, in June 1942, Japan captured Attu and neighboring Kiska, displacing the island’s indigenous Unangan people. The Kotohira Maru is now symbolic of the removal of the people, and the SS Dellwood is similarly representative of the military buildup that prevented their return.

“The documentation of these sunken vessels not only sheds light on their final moments,” the authors wrote, “but it can also be used to bring renewed awareness of Alaska’s World War II history and inform cultural resource managers on Attu’s submerged heritage.”