Complex sentence: From 19 December 1941 to 4 May 1942 "Cummings" escorted convoys between Pearl Harbor and San Francisco, then sailed between Suva, Fiji Islands, and Auckland, New Zealand., from 9 June to 13 August on similar duty.
Split into simpler sentences: From 19 December 1941 to 4 May 1942, "Cummings" escorted convoys between Pearl Harbor and San Francisco. Then sailed between Suva, Fiji Islands, and Auckland, New Zealand, from 9 June to 13 August on similar duty.