Loggerhead's first war patrol started 15 May when she departed Hawaii and headed via Saipan for the Luzon Straits and the South China Sea.

Patrolling along the east coast of Hainan Island, she sighted an enemy hospital ship 11 June and allowed it to pass unharmed.

Three days later, Loggerhead bombarded a suspected radar installation at Gap Rock south of Hong Kong, causing severe damage to the tower.

Changing patrol areas and briefly stopping at Subic Bay 1 July for fuel, the submarine headed for an assigned lifeguard station south of Hong Kong.

The end of hostilities on 15 August found Loggerhead two days out of Fremantle heading for the Gulf of Siam on her second war patrol.