She shuttled from Eniwetok to the fueling areas throughout the campaigns for Saipan, Tinian, and Guam, until moving to Manus, largest of the Admiralty Islands, 20 August.

From Manus, she continued carrying fuel and other supplies to fast carrier groups through the Battle of Peleliu and the first phase of the Philippine Campaign.

By 20 October, when Manatee departed Manus for the last time, the atoll Ulithi at the western edge of the Caroline Islands had been secured and established as a regional center for fleet oilers.

Her fueling activities kept her in the Philippines until late February 1945, when she returned to Ulithi, where three months earlier one of the Manatee's sister ships, the oiler Mississinewa, had been sunk by a Kaiten.

On 2 July, Manatee was ordered to join other fast oilers in lending close support to carrier groups during strikes on the Japanese home islands.

Efficient organization and rapid routing of empty oilers to Ulithi for refueling resulted in an ample supply of fuel oil for the fleet carrier forces.

With the formal cessation of hostilities in the Asiatic-Pacific Theater on 15 August 1945, Manatee sailed for Ulithi en route to San Pedro, California, arriving there on 7 October.

On this voyage the oiler was loaded at Ras Tanura, Arabia, and off-loaded at Norfolk, Virginia, having arrived 17 November via the Suez Canal and Gibraltar.

The following year, after her four months WestPac duty, Manatee was chosen, because of consistently efficient service, to take part in a joint Canadian-American replenishment demonstration held 8 October 1959 for the 14th Annual Conference of the National Defense Transportation Association.

South China Sea operations also occupied most of her 1966, 1967, and 1968 tours, replenishing the ships of the 7th Fleet on patrol in that area in support of the Vietnam War.

[citation needed] After refueling the aircraft carrier USS Ticonderoga off the southern California coast on 20 August 1971; a valve on the Manatee was left open and about 230,000 gallons of heavy fuel oil were spilled.

[4] The large spill created an oil slick that washed ashore, affecting a 65-mile (105 km) stretch of beaches from the Mexican border northward to San Clemente, California, where President Richard Nixon was vacationing at his home there, a residence that reporters at the time often referred to as the "Western White House".