Kōshū Maru

In 1944, Kōshū Maru became one of the largest Hellship disasters involving Asian forced laborers and Allied prisoners of war. A Japanese transport sailing from Batavia, Java, toward Makassar, Celebes, it carried about 1,513 prisoners of war and laborers, most of them Javanese romusha, together with other passengers and air-base supplies. On 4 August 1944, in the Celebes Sea, the unmarked ship was torpedoed and sunk by the American submarine USS Ray, whose crew had no way of knowing prisoners were aboard. Public historical sources indicate that about 1,239 prisoners died, making Kōshū Maru one of the deadliest Japanese POW transport sinkings of 1944.

The Ship

Kōshū Maru was a Japanese passenger-cargo transport employed in wartime convoy service. By mid-1944 it had become part of Japan’s forced-labor and prisoner transport system, carrying both POWs and civilian laborers through dangerous waters under increasing Allied submarine pressure. Like other Hellships, it was not marked to indicate that prisoners were aboard, even though it was operating in a combat zone where Japanese shipping was under active attack.

The Voyage

Public voyage summaries indicate that Kōshū Maru departed Batavia, Java, on 29 July 1944 for Makassar, Celebes, carrying 1,513 prisoners of war/laborers. The West Point voyage list gives the same Batavia departure and Makassar destination, while the POW Research Network notes that in addition to the Javanese romusha, the ship was also carrying 540 passengers and air-base supplies. Other public summaries describe the human cargo as mostly Javanese laborers intended for work on the bombed airstrip at Makassar, with a smaller number of Allied POWs also aboard.

The Attack or Loss

On 4 August 1944, USS Ray (SS-271) attacked a Japanese convoy bound for Makassar in the Celebes Sea and sank Kōshū Maru. Wrecksite’s vessel summary and the POW Research Network both identify that date and attack, and the Imperial War Museums includes Kōshū Maru among the POW transport ships sunk by Allied forces in East Asia. Because the ship was unmarked, the American submarine had no way of distinguishing it from any other Japanese transport.

Casualties and Survivors

The public casualty figures for Kōshū Maru are unusually consistent. The West Point voyage list states 1,513 aboard and 690 survivors, implying 823 dead overall, but other specialized Hellship sources make clear that the POW/laborer losses were much higher. The POW Research Network states that 1,239 of the prisoners and laborers died, and Mansell’s Hell Ship losses page also gives 1,239 forced laborers dead. These different totals likely reflect the difference between all persons aboard and the prisoner/laborer subgroup. For page purposes, the clearest formulation is that Kōshū Maru carried 1,513 POWs and laborers, most of them Javanese romusha, and about 1,239 of them died in the sinking.

Legacy and Memorialization

Kōshū Maru is important in Hellship history because it underscores that these tragedies did not involve Allied military prisoners alone. Like Jun’yō Maru, its dead included very large numbers of Asian forced laborers, especially Javanese romusha, whose suffering has often received less attention in Western wartime narratives. The Imperial War Museums places Kōshū Maru among the wider history of POW transport sinkings in East Asia, while Japanese POW research databases preserve the basic voyage and loss details. Today, the ship’s story remains important both for Hellship scholarship and for broader efforts to recognize the human cost borne by Asian civilian laborers caught in Japan’s wartime transport system.

Sources

POW Research Network Japan, Kōshū Maru.
Imperial War Museums, The Sinking of Prisoner of War Transport Ships in East Asia.
West Point, List of Hellship Voyages.
Mansell, Hell Ship Major Losses.
Japanese POW camps and Hell Ships booklet summary.

Harugiku Maru
Jun’yō Maru
Tamahoko Maru
Suez Maru
Hellships Casualty Database
Hellships Survivor Records
Hellships Research Center
Hellships Researcher Guide