The flotilla was initially used in anti-submarine patrols around Guadalcanal's Cape Esperance and on 29 January 1943, "Moa" along with her sister ship "Kiwi", sank the Japanese submarine "I-1" which was supporting Operation Ke during the Guadalcanal Campaign. Both ships were patrolling at Guadalcanal and "Kiwi"s depth-charge attack brought the submarine to the surface. She attempted to escape but was rammed by "Kiwi" while "Moa" continued to provide illumination with star shells. "Moa" pursued and pressed home the attack upon the I-1, which eventually ran aground on a reef. Two days later, "Moa" attacked Japanese landing barges, sinking one of them. Phipps was awarded a bar to his DSC and the United States Navy Cross for these actions.