During the spring of 1944, American military thinking focused increasingly upon the Central Pacific invasion route to Japan. Accordingly, "Stringham" returned to Hawaii with marines embarked; and both she and her passengers commenced preparations for the invasion of the Marianas. The initial waves of assault troops stormed the beaches at Saipan on 15 June. "Stringham" discharged her marines the following day and patrolled off Saipan throughout the Battle of the Philippine Sea on 19 and 20 June. On 22 June, Underwater Demolition Team (UDT) 7 shifted to her from for the Tinian phase of the Marianas operation. Until the landings, the high-speed transport conducted sporadic bombardment and harassment fire on Tinian. On 10 July, she sent her UDT men ashore to reconnoiter the two potential landing sites; and, just before the actual assault began on 24 July, her frogmen participated in a daylight feint at Tinian Town to divert Japanese attention from the actual landing sites. On 28 July, she completed her work with UDT 7 in the Marianas and headed for Espiritu Santo, via Eniwetok Atoll.