The regiment relieved the 4th Marines on Emirau Island on 11 April 1944 and performed garrison duties until they were relieved by the 369th Infantry Regiment in June. While they were on Emirau, they assisted the US Navy Seabees in constructing an airfield, because the 147th was the only infantry regiment who'd constructed an airfield before (at Tonga in 1942). The regiment then moved to the island of Saipan in the wake of the first landings to conduct mopping up operations behind the 2nd Marine Division, the 4th Marine Division, and the 27th Infantry Division. The island was declared secure on 9 July 1944, but Japanese resistance continued for months afterward. The 147th next moved to the island of Tinian to follow elements of the 2nd and 4th Marine Divisions as they assaulted through the island. The 147th rooted out stubborn Japanese defenders and continued fighting after the island was officially declared secure on 1 August 1944.