"Merrimack" departed Norfolk, Virginia, on 14 October 1944 for the Panama Canal and Ulithi in the Pacific, arriving on 1 December 1944. Allied forces were retaking the Philippine Islands and preparing for operations even closer to the Japanese Home Islands. "Merrimack" joined the United States Third Fleet's At-Sea Logistics Support Group to fuel the fast carrier task force. She began the new year of 1945 supporting raids on Formosa on 3 and 4 January 1945. The U.S. carriers struck enemy airbases on Luzon, Philippines, on 6 and 7 January to help neutralize Japanese resistance to the invasion of that strategic island which began on the beaches of Lingayen Gulf on 9 January 1945. Naval aircraft which she supported returned to Formosa on the 15th and hit targets along the China coast the following day. They again lashed out at Formosa on the 21st.