The Marianas operation involved the invasion of Saipan, Tinian, and Guam by forces under Admiral Raymond A. Spruance. "Walker" began service assigned to an escort carrier unit providing air support for the amphibious forces headed for Guam. The group departed from Kwajalein in June; but, due to the bitterness of the campaign for Saipan, the Guam landings were postponed, and the ships returned to Eniwetok. After the need for further naval support had passed, "Walker" proceeded to Pearl Harbor for rehearsals of scheduled landings on Yap Island.