page_title: Convoy GP55
section_title: Aftermath
hierarchical_section_title: Convoy GP55 / Aftermath
caption_attribution_description: English: Australian Bathurst class corvette HMAS Deloraine
context_page_description: Convoy GP55 was a convoy of Allied ships that travelled from Sydney to Brisbane in June 1943 during World War II. It comprised ten cargo ships, three landing ships, tank and an escort of five corvettes. The Japanese submarine I-174 attacked the convoy on 16 June, sinking the United States Army transport ship Portmar and damaging USS LST-469. Two of the corvettes counter-attacked I-174, but only lightly damaged her.
  The Australian military conducted an intensive search for I-174 in the days after the attack in the mistaken belief that she had been significantly damaged. This search was not successful and highlighted the unsatisfactory communications between the Royal Australian Navy and Royal Australian Air Force. However, another Japanese submarine passing through the area may have been sunk by RAAF aircraft. Because of Japan's deteriorating strategic situation, I-174 was the last Imperial Japanese Navy submarine to operate off the Australian east coast.
context_section_description: Following the attack, the Australian Chief of Naval Staff, Admiral Sir Guy Royle, judged that the submarine had been damaged and ordered that "special measures" be taken to search for it. The RAAF commenced air searches of an 80-square-nautical-mile (270 km²) box south-east of Coffs Harbour on the night of 16/17 June, while Deloraine, Kalgoorlie and the recently arrived destroyer HMAS Vendetta patrolled the area. On 17 June, Anson aircraft were assigned to patrol the submarine's most likely escape routes in the hope that this would force her to remain submerged during the day and surface at night. Radar-equipped Beauforts relieved the Ansons after dusk and continued the search.
  In the early morning of 18 June, two No. 32 Squadron Beauforts attacked with bombs and gunfire what they took to be a submarine. Deloraine was less than 6 miles (9.7 km) from the area of the RAAF attack, but did not acknowledge repeated attempts by the aircraft to communicate with her. The Beauforts reported that they had damaged the submarine and intensive efforts were made on 19 June to locate and sink her, with twelve Ansons continuously sweeping the area while six Vengeance dive bombers were held in readiness nearby. No further sightings were made and it was assumed that the submarine had been damaged by a No. 32 Squadron aircraft but escaped. Naval historian David Stevens has written that the sighting made on 18 June was probably mistaken, as I-174 was at least 60 miles (97 km) to the east of where the RAAF attack took place and the incident was not recorded in her war diary. However, other historians believe that the Beauforts may have sunk I-178, which was patrolling off the east coast of Australia at the time; this submarine disappeared some time after 17 June 1943, and the cause of her loss has never been confirmed. I-174 was ordered to depart from Australian waters on 20 June, and returned to Truk on 1 July. She did not make contact with any Allied ships or aircraft after attacking GP55.
  The seeming failure of the RAAF and RAN to cooperate to finish off a damaged submarine led Royle to order an inquiry into the attack. This found that a breakdown in communication between the two services was the main cause of the failure, with both the aircraft and the naval signal room in Sydney making procedural errors. Rear Admiral Gerard Muirhead-Gould, the naval officer in command of the Sydney region, also noted that communications between the RAN and RAAF were unsatisfactory at higher levels, and that the communication procedures to be used in anti-submarine operations were not well known or understood. In response, he suggested that the RAN establish the position of Commander Escort Vessels Group to organise and command escorts and coordinate their tactics.
  The attack on Convoy GP55 was the last attack made by a Japanese submarine on the east coast of Australia. Two submarines were dispatched to operate off Australia in July 1943, but were diverted to the Solomon Islands shortly before reaching the east coast. Following this, the Japanese submarines were fully occupied responding to Allied offensives and transporting supplies to isolated garrisons. As the threat to shipping declined, the RAN ceased running convoys in waters south of Newcastle on 7 December 1943 and Sydney–Brisbane convoys ended on 10 February 1944.
caption: HMAS Deloraine
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