By April 1942, the Japanese had consolidated their hold on Rabaul. It was supposed to be their fortress from which they would extend by force their dominion over the Solomons and New Guinea. That was the master plan. But the Coral Sea and Midway battles had cost them five aircraft carriers and most of their finest pilots. In mid-June 1942, Admiral Yamamoto decided they needed to change strategies. Their focus shifted to defending their present holdings in the South Pacific and New Guinea. Planned offensive operations were cancelled. The awakening of the sleeping giant he had predicted was happening. The Americans seemed to have a limitless supply of planes and pilots. And they seemed to be everywhere.
At Rabaul, it began to dawn on the Japanese that they had concentrated on the delivery of troops, weapons, and ammunition rather than food. By May 1942, food stockpiles were extremely low. There was not enough to feed both their military and the Australian prisoners kept at Rabaul. Therefore 1053 of these Australian “Guests of the Emperor” – 850 troops and 203 civilians – would be sent to work in rear echelons at Samah on Hainan Island.
On June 22, 1942, the cargo transport Montevideo Maru sailed from Rabaul with the 1053 Australians aboard. On July 1, 1942, at 0326 hours, as the Montevideo Maru exited Babuyan Channel, off the coast of Luzon Island, at 18-35N, 120-25E, she crossed paths with the American submarine USS Sturgeon (SS-187). Unaware of her human cargo, the submerged Sturgeon fired four torpedoes at the 7,266-ton cargo transport. Two of the torpedoes hit the Montevideo Maru’s starboard side, ripping open her two aft holds and igniting a secondary explosion in her fuel tank. She sank by the stern in under eleven minutes. All the Australian prisoners drowned. Eleven passengers and nine crew were killed. Survivors in two lifeboats landed near Cape Bojeador on July 2nd and from there made it to Bobon village the next day. Fifty-five of the survivors were killed by Filipino natives. On July 5th, one survivor reached Laoag. On July 25th, Japanese rescuers recovered a total of 21 starving and exhausted survivors.
The Sturgeon’s crew celebrated the sinking of this large enemy merchantman. They had no idea they had caused the worst maritime disaster in Australian history.