After shakedown out of San Diego, the escort carrier sailed on 7 February 1944 with 400 troops embarked for Pearl Harbor, thence to rendezvous off the Marshalls, guarded by the destroyer Norman Scott, where she flew 84 replacement planes to the fleet carrier Enterprise.
She returned to San Diego via Pearl Harbor, ferrying aircraft for repairs and qualified carrier pilots off the coast of Southern California.
She departed on 1 May to join Rear Admiral Harold B. Sallada's Carrier Support Group 2 (TG 52.11), staging in the Marshalls for the invasion of the Marianas.

Gambier Bay gave close air support to the initial landings of Marines on Saipan 15 June 1944, destroying enemy gun emplacements, troops, tanks, and trucks.
On the 17th, her combat air patrol (CAP) shot down or turned back all but a handful of 47 enemy planes headed for her task group and her gunners shot down two of the three planes that did break through to attack her.

The following day, warning of another air attack sounded.
As her fighters prepared to take off, they found intense antiaircraft fire of the entire task group covering their flight path.
Captain Goodwin called the event "another shining example of the adaptability and courage of the young men of our country".
Eight pilots of Composite Squadron 10 (VC-10) did take off to help repulse the aerial attack.

Gambier Bay remained off Saipan, repulsing aerial raids and launching planes which strafed enemy troop concentrations, bombed gun emplacements, and supported Marines and soldiers fighting ashore.
Meanwhile, American carriers slashed the carrier air strength of the combined Japanese Mobile Fleet and turned it back in defeat in the Battle of the Philippine Sea.
Gambier Bay continued close ground support operations at Tinian (19–31 July), then turned her attention to Guam, where she gave identical aid to invading troops until 11 August.

After a respite for logistics in the Marshalls, Gambier Bay spent 15–28 September supporting the amphibious attack which drove ashore and captured Peleliu and Angaur, Southern Palaus.
She then steamed by way of Hollandia (currently known as Jayapura), New Guinea, to Manus Island, Admiralties, where the invasion of the Philippines was staged.
Screened by four destroyer escorts, Gambier Bay and her sister ship Kitkun Bay escorted transports and amphibious landing ships safely to Leyte Gulf before joining Rear Admiral Clifton A. F. Sprague's escort carrier task unit on 19 September off Leyte.

The task unit comprised six escort carriers, screened by three destroyers and four destroyer escorts, and was known by its radio call sign: "Taffy 3".
Under the command of Rear Admiral Thomas L. Sprague, 18 escort carriers—divided into three, six-carrier task units ("Taffy"s)—maintained air supremacy over Leyte Gulf and eastern Leyte.
During the invasion their planes destroyed enemy airfields, supply convoys, and troop concentrations; gave troops driving inland vital close air support; and maintained combat air patrol over ships in Leyte Gulf.
While "Taffy 1" and "Taffy 2" were respectively stationed off northern Mindanao and off the entrance to Leyte Gulf, "Taffy 3" steamed off Samar.

Meanwhile, the Japanese threw their entire fleet against American naval power in a desperate gamble to destroy the large concentration of American shipping in Leyte Gulf.
Powerful Japanese forces—composed of carriers, battleships, cruisers, and destroyers—attempted to converge on the Philippines in a three-pronged attack to the south, center, and north.
The Japanese Southern Force met disaster before dawn on 25 October as it tried to drive through Surigao Strait to join the Center Force off Leyte Gulf.
While steaming through the Sibuyan Sea en route to the San Bernardino Strait on 24 October, the Center Force was hit hard by hundreds of planes from the carriers of Admiral William "Bull" Halsey′s 3rd Fleet.
After the Battle of Sibuyan Sea, Admiral Halsey no longer considered the Center Force a serious threat, and he sent the carriers north to intercept decoy carriers of the Japanese Northern Force off Cap
After shakedown out of San Diego, the escort carrier sailed on 7 February 1944 with 400 troops embarked for Pearl Harbor, thence to rendezvous off the Marshalls, guarded by the destroyer Norman Scott, where she flew 84 replacement planes to the fleet carrier Enterprise. She returned to San Diego via Pearl Harbor, ferrying aircraft for repairs and qualified carrier pilots off the coast of Southern California. She departed on 1 May to join Rear Admiral Harold B. Sallada's Carrier Support Group 2 (TG 52.11), staging in the Marshalls for the invasion of the Marianas.
Gambier Bay gave close air support to the initial landings of Marines on Saipan 15 June 1944, destroying enemy gun emplacements, troops, tanks, and trucks. On the 17th, her combat air patrol (CAP) shot down or turned back all but a handful of 47 enemy planes headed for her task group and her gunners shot down two of the three planes that did break through to attack her.
The following day, warning of another air attack sounded. As her fighters prepared to take off, they found intense antiaircraft fire of the entire task group covering their flight path. Captain Goodwin called the event "another shining example of the adaptability and courage of the young men of our country". Eight pilots of Composite Squadron 10 (VC-10) did take off to help repulse the aerial attack.
Gambier Bay remained off Saipan, repulsing aerial raids and launching planes which strafed enemy troop concentrations, bombed gun emplacements, and supported Marines and soldiers fighting ashore. Meanwhile, American carriers slashed the carrier air strength of the combined Japanese Mobile Fleet and turned it back in defeat in the Battle of the Philippine Sea. Gambier Bay continued close ground support operations at Tinian (19–31 July), then turned her attention to Guam, where she gave identical aid to invading troops until 11 August.
After a respite for logistics in the Marshalls, Gambier Bay spent 15–28 September supporting the amphibious attack which drove ashore and captured Peleliu and Angaur, Southern Palaus. She then steamed by way of Hollandia (currently known as Jayapura), New Guinea, to Manus Island, Admiralties, where the invasion of the Philippines was staged. Screened by four destroyer escorts, Gambier Bay and her sister ship Kitkun Bay escorted transports and amphibious landing ships safely to Leyte Gulf before joining Rear Admiral Clifton A. F. Sprague's escort carrier task unit on 19 September off Leyte.
The task unit comprised six escort carriers, screened by three destroyers and four destroyer escorts, and was known by its radio call sign: "Taffy 3". Under the command of Rear Admiral Thomas L. Sprague, 18 escort carriers—divided into three, six-carrier task units ("Taffy"s)—maintained air supremacy over Leyte Gulf and eastern Leyte. During the invasion their planes destroyed enemy airfields, supply convoys, and troop concentrations; gave troops driving inland vital close air support; and maintained combat air patrol over ships in Leyte Gulf. While "Taffy 1" and "Taffy 2" were respectively stationed off northern Mindanao and off the entrance to Leyte Gulf, "Taffy 3" steamed off Samar.
Meanwhile, the Japanese threw their entire fleet against American naval power in a desperate gamble to destroy the large concentration of American shipping in Leyte Gulf. Powerful Japanese forces—composed of carriers, battleships, cruisers, and destroyers—attempted to converge on the Philippines in a three-pronged attack to the south, center, and north. The Japanese Southern Force met disaster before dawn on 25 October as it tried to drive through Surigao Strait to join the Center Force off Leyte Gulf. While steaming through the Sibuyan Sea en route to the San Bernardino Strait on 24 October, the Center Force was hit hard by hundreds of planes from the carriers of Admiral William "Bull" Halsey′s 3rd Fleet. After the Battle of Sibuyan Sea, Admiral Halsey no longer considered the Center Force a serious threat, and he sent the carriers north to intercept decoy carriers of the Japanese Northern Force off Cap
USS Gambier Bay