Throughout November and December 1944 and January 1945 she replenished Task Force 38. This Task Force struck the enemy devastating blows at Luzon, Formosa, the China Coast, and French Indochina. Departing Ulithi on 8 February, she steamed northward and remained at sea until 3 March to refuel carriers, battleships, cruisers, and destroyers of the 5th Fleet engaged in the savage struggle for Iwo Jima and the supporting carrier air strikes on Tokyo. After renewing her cargo at Ulithi, she sailed on 13 March to supply carriers, including and as they were conducting air strikes on Kyūshū, the Inland Sea, and the Ryukyus. On 1 April, as landings on Okinawa progressed, "Kankakee" departed Southern Anchorage, Ulithi, for logistic support duty off Okinawa. Under the operational command of Rear Admiral Donald B. Beary, Commander ServRon 6, she furnished fuel and supplies at sea to ships of the 5th Fleet. During much of the next three months she helped maintain their striking power and mobility in the last great amphibious campaign of the war. Completing her Ryukyus duty on 14 June, she resumed support on 3 July for the 3rd Fleet as Task Force 38 conducted devastating aerial and naval bombardments on the "home islands" from Hokkaidō to the Inland Sea. "Kankakee" steamed southeast of Japan as offensive operations ceased on 15 August; but she maintained logistic support until her return to Ulithi on 5 September. After putting into Tokyo Bay on 20 September, she proceeded to the United States, arriving San Pedro on 18 November for overhaul.