Following her accelerated builder's trials and shakedown cruise, "Essex" moved to the Pacific in May 1943. Departing from Pearl Harbor, she participated with Task Force 16 (TF 16) in carrier operations against Marcus Island. On 31August 1943, she was designated the flagship of TF14 and struck Wake Island on 5and6 October. On 11November, she took part in carrier operations during the Rabaul strike, alongside and . She then launched an attack with Task Group 50.3 (TG50.3) against the Gilbert Islands where she took part in her first amphibious assault during the Battle of Tarawa. After refueling at sea, she cruised as the flagship of TG50.3 to attack Kwajalein on 4 December. Her second amphibious assault delivered in company with TG50.3 was against the Marshall Islands on 29January to 2February 1944.