Allied intelligence and military actions’ impact on the fate of Japanese "hell ships" during World War II
Allied intelligence and military actions significantly impacted the fate of Japanese "hell ships" during World War II, though often with tragic unintended consequences for the Allied prisoners of war (POWs) onboard. These hell ships were Japanese merchant vessels, requisitioned by the Imperial Japanese Navy and Army, to transport Allied POWs and Asian forced slave laborers from occupied territories to various locations for forced labor, under extremely inhumane conditions.
Allied Intelligence Efforts
Allied intelligence played a crucial role in identifying and tracking these ships:
• Intercepted Radio Transmissions Allied forces relied most heavily on intercepted radio transmissions from Japanese ship commanders, who sent two daily communications to their general headquarters, including POW counts.
• Joint Intelligence Center Pacific Ocean Area (JICPOA) Established in September 1943, JICPOA was responsible for intercepting, decoding, and acting on these transmissions. Intelligence units in Australia, Bletchley Park (England), Delhi (India), and Colombo (Ceylon/Sri Lanka) contributed to the decryption and translation efforts.
• Actionable Intelligence and Ultras The intelligence gathered was compiled into "Ultras" (ultrasecret communiqués) for theater commanders. However, details about the presence of POWs were typically excised during this process, meaning individual ship commanders at sea were usually unaware that their targets carried Allied prisoners or Japanese civilians.
• Increased Activity in 1944 Intelligence gathering intensified in 1944, particularly around the Philippines, as the Japanese scrambled to move resources and people, including POWs, to the Japanese Home Islands due to the American advance. This led to a surge in intercepted messages.
Allied Military Actions and Their Impact
Despite the intelligence, the military actions taken against these ships often resulted in high casualties among the POWs:
• Justification for Attacks Japanese hell ships were considered legitimate targets because they transported a mixture of POWs, regular Japanese troops, and vital cargo for the Japanese war effort, and were therefore not marked as non-combatants.
• Primary Attackers The majority of these attacks were carried out by the United States Navy, with assistance from Allied intelligence services and the Royal Navy's British Pacific Fleet.
• Method of Attack Allied submarines and aircraft engaged these vessels using torpedoes, bombs, and strafing.
Tragic Consequences for POWs
The conditions on board were already abysmal, with POWs denied adequate food, water, and sanitation, leading to deaths from dehydration, hyperthermia, starvation, and violence. However, the greatest cause of fatalities for POWs on these ships were unintended Allied attacks, which killed thousands.
• Overall Casualties Out of approximately 126,000 Allied POWs transported on 134 Japanese hell ships over 156 voyages, more than 19,000 deaths were a direct consequence of Allied attacks, compared to about 1,540 deaths from the inhumane conditions and violence onboard.
Several notable incidents illustrate this tragic impact:
• Montevideo Maru On July 1, 1942, the USS Sturgeon sank the Montevideo Maru, resulting in the drowning of over 1,000 Australian troops and 200 administrative personnel.
• Lisbon Maru Torpedoed by USS Grouper on October 1, 1942, the Lisbon Maru sank the following day, killing 800 of the 2,000 British POWs aboard. Many who attempted to escape were also shot by Japanese guards.
• Suez Maru On November 29, 1943, USS Bonefish torpedoed the Suez Maru. Most of the 548 British and Dutch POWs drowned in the holds, and those who escaped the sinking ship were shot by Japanese guards. A Japanese minesweeper also machine-gunned a minimum of 250 surviving POWs in the water, leading to no POW survivors.
• Jun'yō Maru On September 18, 1944, HMS Tradewind torpedoed the Jun'yō Maru, leading to the deaths of about 4,000 romushas (slave laborers) and 1,626 POWs.
• Hofuku Maru Sunk by American aircraft on September 21, 1944, the Hofuku Maru lost 1,047 of its 1,289 British and Dutch POWs.
• Shinyo Maru On September 7, 1944, USS Paddle attacked the Shinyo Maru, sinking it and killing 687 Allied POWs. Japanese guards also fired on prisoners attempting to abandon ship.
• Oryoku Maru This ship, which left Manila on December 13, 1944, with 1,620 POWs (mostly American survivors of the Bataan Death March) packed into its holds, was bombed and strafed by U.S. Navy planes from USS Hornet and USS Cabot on December 14 and 15, causing it to sink. About 270 died on board from suffocation, dehydration, or being killed in the attack or shot while escaping. Survivors faced further mistreatment and subsequent bombings on other hell ships like the Enoura Maru and Brazil Maru, with only 128 of the original 1,620 POWs surviving the war.
The decision to target these vessels highlights the complexity of wartime decisions and intelligence limitations, where strategic imperatives overshadowed the knowledge of human cargo, contributing to immense suffering and loss of life. The Japanese perspective of treating Western prisoners as mere commodities also justified the inhumane conditions aboard these ships.
