The ships were capable of a top speed of 19 knots (35 km/h; 22 mph), and due to their origin as tankers, had extensive fuel storage.

In 1941, as United States participation in World War II became increasingly likely, the US Navy embarked on a construction program for escort carriers, which were converted from transport ships of various types.

These proved to be very successful ships, and the Commencement Bay class, authorized for Fiscal Year 1944, were an improved version of the Sangamon design.

[1] They proved to be the most successful of the escort carriers, and the only class to be retained in active service after the war, since they were large enough to operate newer aircraft.

Given the very large storage capacity for oil, the ships of the Commencement Bay class could steam for some 23,900 nautical miles (44,300 km; 27,500 mi) at a speed of 15 knots (28 km/h; 17 mph).

She was finally ready for service on 3 September, the day after the surrender of Japan formally ended World War II.

While en route, her orders were changed, directing her to join her sister ships Siboney and Puget Sound in the Mariana Islands in the central Pacific.

Bairoko carried out fight testing of the new aircraft until 26 April, when the ship was removed from active service due to crew shortages.

The ship was back in service by 24 January 1947, and she cruised in the local area until 17 February, when she departed for Pearl Harbor to take on a load of aircraft she was to ferry to other carriers participating in fleet problem 2-47, which was held between 2 and 9 March.

[6] Bairoko moved to San Pedro on 7 January 1948 for further modifications, this time receiving a decontamination center on her hangar deck and a repair facility for scientific instruments.

The ship left San Pedro on 17 February, carrying a load of reconnaissance planes, support helicopters, and scientists from the Radiological Safety Group.

[6] The ship spent the rest of the year conducting, pilot qualifications, anti-submarine training exercises, and other maneuvers off the coast of California.

[6] On 10 May 1951, while in Yokosuka, Japan, an explosion rocked the ship, starting a major fire in her hangar that quickly spread to the engine room.

Five men were killed in the blaze, which badly damaged the ship, destroying ventilation and electrical systems and weakening internal bulkheads.

Five days later, she arrived in her patrol area in the Yellow Sea, escorted by the British destroyers HMS Charity and Cossack.

The ship's fighters carried out patrols over southern North Korea over the next nine days, attacking any targets of opportunity they encountered, including bridges, gun positions, and supply vehicles.

[6] On 18 April, the British aircraft carrier HMS Glory arrived to relieve Bairoko off the western coast of Korea, allowing the latter vessel to return to Japan.

Once again carrying VMA-312, the carrier launched a total of 183 sorties during this period, which included raids on enemy positions, aerial reconnaissance, and combat air patrols.

The work lasted some seven weeks, after which Bairoko returned to San Diego to begin preparations for her role in Operation Castle, a major nuclear weapons test at Eniwetok and Bikini Atoll that included a series of six detonations.

The ship spent the rest of 1953 and early 1954 loading radiological equipment and observation aircraft, including six photo-reconnaissance Corsairs from VC-3 and twelve helicopters from HMR-362.

[6] On 20 January, Bairoko arrived in Kwajalein, where she provided air transport to workers who were preparing facilities for the tests on Bikini and Eniwetok.

Her aircraft flew observation missions during the blasts to conduct radiological surveys of the area, and the ship herself served as a decontamination center.

On 1 March, the Castle Bravo detonation significantly exceeded expectations, showering Bairoko—which was some 38 nautical miles (70 km; 44 mi) away—with highly radioactive nuclear fallout.

The ship's ventilation system was sealed to prevent contamination, but sixteen of her crew were nevertheless exposed to the radioactive dust and received radiation burns.

The fallout also reached the Japanese fishing boat Daigo Fukuryū Maru, which was about 90 nautical miles (170 km; 100 mi) away, and burned 23 of her crew.

[6] By this time, the Navy had begun replacing the Commencement Bay-class ships with much larger Essex-class aircraft carriers, since the former were too small to operate newer and more effective anti-submarine patrol planes.

Proposals to radically rebuild the Commencement Bays either with an angled flight deck and various structural improvements or lengthen their hulls by 30 ft (9.1 m) and replace their propulsion machinery to increase speed came to nothing, as they were deemed to be too expensive.