In January 1944, Vice Admiral Marc Mitscher made the "Yorktown" his flagship. Mitcher was impressed with Clark's seamanship and fighting spirit. In February 1944, Clark was promoted to rear admiral and was transferred temporarily to Task Force 58 while still reporting to Mitscher, who was then commanding the Fast Carrier Task Force, and Admiral Raymond Spruance, commander of the Fifth Fleet. Since all of the task group's command slots were occupied, Clark was assigned to command the new aircraft carrier, , also named for a sunken carrier (USS Hornet CV-8). Soon, Mitscher was disappointed with the performance of the vice admiral commanding Task Group 3, and replaced him with Captain Clark. He commanded this group in the Marianas campaign, and on multiple occasions his task group was sent north to interdict Japanese aircraft shuttling down from Japan via intermediate islands. His air groups executed air attacks on the shuttle islands of Chichi Jima and Iwo Jima so often that the sailors of the Fast Carrier Task Force nicknamed them the "Jocko Jimas."