Allied Submarines Involved in Hellship Attacks

During World War II, Allied submarines played a critical role in the campaign to destroy Japanese shipping across the Pacific. American and British submarines were tasked with cutting Japan’s maritime supply lines, which were essential for transporting troops, raw materials, and military equipment across the empire. In carrying out these missions, Allied submarines attacked hundreds of Japanese merchant ships. Tragically, some of these vessels were transporting Allied prisoners of war. Because the ships were unmarked and indistinguishable from ordinary cargo transports, submarine crews had no way of knowing that prisoners were aboard.

The Japanese decision to transport prisoners in ordinary merchant vessels created a deadly situation. As the war intensified, Japan increasingly relied on its merchant fleet to move prisoners captured in Southeast Asia and the Philippines to labor camps in Taiwan, China, and Japan. These ships later became known as Hellships due to the brutal conditions endured by prisoners during the voyages. When Allied submarines encountered these transports, they treated them as legitimate military targets within the broader effort to cripple Japan’s wartime logistics.

The Submarine Campaign Against Japanese Shipping

The submarine campaign against Japanese shipping was one of the most effective Allied strategies in the Pacific War. By 1944, American submarines had begun systematically destroying Japan’s merchant fleet. These attacks severely disrupted Japan’s ability to move supplies and personnel across the Pacific.

Submarine patrols targeted Japanese convoys traveling through major shipping corridors such as:

  • the South China Sea

  • the East China Sea

  • waters around Taiwan

  • the approaches to the Japanese home islands

Many Hellships traveled along these same routes, placing them directly in the path of Allied submarine patrols.

Submarines Associated with Hellship Sinkings

Several Allied submarines are known to have sunk ships carrying prisoners of war. In nearly every case, the submarine crews were unaware that POWs were aboard.

USS Shark (SS-314)

The American submarine USS Shark (SS-314) torpedoed the Japanese transport Arisan Maru in October 1944. The ship was carrying more than 1,700 American prisoners of war from the Philippines to Japan. The sinking resulted in the largest loss of American POW lives at sea during World War II.

HMS Tradewind

The British submarine HMS Tradewind sank the Japanese transport Junyo Maru in September 1944 off the coast of Sumatra. The ship carried more than 6,000 prisoners of war and forced laborers, making it one of the deadliest maritime disasters of the war.

USS Pampan (SS-383)

The American submarine USS Pampan (SS-383) participated in the attack on a Japanese convoy in September 1944 that included the Hellships Rakuyo Maru and Kachidoki Maru. After the attack, Pampan returned to the area and rescued several surviving prisoners from the water—one of the few instances in which POW survivors were recovered by Allied submarines.

USS Sealion (SS-315)

Another American submarine, USS Sealion (SS-315), also attacked the convoy carrying Rakuyo Maru. The coordinated submarine attack destroyed multiple Japanese transports, including vessels carrying prisoners.

USS Grouper (SS-214)

The American submarine USS Grouper (SS-214) torpedoed the Japanese transport Lisbon Maru in October 1942 while it was carrying more than 1,800 British prisoners of war captured in Hong Kong.

USS Sturgeon (SS-187)

The submarine USS Sturgeon (SS-187) sank the Japanese transport Montevideo Maru in July 1942. The ship carried more than 1,000 prisoners and civilian internees captured during the fall of Rabaul.

The Tragedy of Unmarked POW Transports

These sinkings illustrate the tragic consequences of transporting prisoners aboard unmarked ships in a war zone. Allied submarines were operating under orders to attack Japanese merchant shipping wherever it could be found. Without markings or advance intelligence indicating that prisoners were aboard, submarine commanders had no way of distinguishing Hellships from ordinary cargo vessels.

After the war, the scale of the Hellship tragedies became more widely understood as survivor testimony and archival records were examined. Many submarine commanders later expressed deep regret upon learning that their attacks had unintentionally caused the deaths of Allied prisoners.

Remembering the Victims

Today the sinkings of Hellships are remembered as part of the broader history of the Pacific War. They reflect both the brutal conditions endured by prisoners and the realities of naval warfare in which ships carrying POWs were hidden among ordinary merchant transports.

The story of the Hellships also highlights the importance of historical research and remembrance. By studying these events and documenting the ships involved, historians and memorial organizations continue to preserve the memory of the prisoners who lost their lives during these voyages.