"Guest" poured gunfire ahead of troops landing on Saipan 15 June 1944, then helped repel four massive air raids against Admiral Marc Mitscher's Fast Carrier Task Force in the Battle of the Philippine Sea. She also conducted pre-invasion bombardment of Guam and gave direct gunfire support to the landings on Guam 21 July 1944. She remained on bombardment support and patrol stations until 9 August, then sailed for amphibious warfare exercises in the Solomons.