evaded a retaliatory depth charge attack. Soon afterward, the submarine returned to Fremantle, ending another patrol on 5 December. Third and fourth war patrols, December 1944 – May 1945 Putting to sea again 24 December, Hardhead began her third war patrol in the South China Sea. Operating with and , Hardhead damaged several ships before sinking Nanshin Maru 2 February 1945. Following lifeguard duty for the B-29 strikes on Singapore she returned to Fremantle 15 February. Hardheads fourth war patrol included a special mine-laying mission. She sailed 20 March 1945 and laid mines off French Indochina during the night of 2 April. The submarine then entered the Gulf of Siam, where after several attacks she sank cargo ship Araosan Maru 6 April. Following a visit to Subic Bay to reload 11 April – 15 April she patrolled the South China Sea, but found few contacts. American submarines had by this time reduced Japanese merchant activity to a trickle, effectively destroying the island nation's lifeline to the outside world. Hardhead returned to Fremantle 16 May. Fifth and sixth war patrols, June – August 1945 Sailing from Fremantle 18 June, Hardhead began her fifth war patrol, to be conducted in the Java Sea. She severely damaged a freighter with her deck guns 22 June, and next day sank four coastal defense craft during an attack on Ambat Roads with including submarine chasers Cha-42 () and Cha-113 (ex-Dutch minesweeper A) () and shuttle boat No. 8333 southeast of the Masalembu Islands. The illness of her commanding officer forced Hardhead to end her fifth patrol 17 July at Onslow, Australia. The submarine departed Onslow on her sixth and last patrol 18 July, and headed back into the Java Sea. On 23 July 1943, she torpedoed and sank the submarine chaser Cha-117 (ex-Dutch Bantam) off the northeast coast of Bali (). She forced a merchant ship to beach 27 July but found few targets and returned to Subic Bay 10 August. Soon afterward the Pacific war ended. Hardhead sailed 31 August and arrived at San Francisco via Pearl Harbor 22 September 1945. She decommissioned 10 May 1946 and entered the Pacific Reserve Fleet at Mare Island. Post-war service, 1952–1972 Hardhead was placed in commission in reserve 6 February 1952 and upon her arrival at New London for conversion was placed out of commission. Following her GUPPY IIA conversion, including streamlining, installation of a snorkel breathing