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).

On 15 August, the Japan announced it would surrender, ending the war; Siboney arrived in Pearl Harbor the following day, and so she unloaded her cargo and remained in Hawaiian waters for the rest of the month.

While on the way, she contributed aircraft to search operations attempting to locate the Martin PBM Mariner that had been carrying Rear Admiral William Sample, which had gone missing on 2 October.

Siboney stopped at various ports on Honshu from 8 to 11 October, before rejoining the search effort, which failed to locate the missing plane.

She was then ordered to return to the United States, by way of Manila in the Philippines; Hong Kong, China; Saipan and Guam in the Mariana Islands; and Pearl Harbor.

She made another voyage into the Mediterranean from September to 14 November, in company with warships from other North Atlantic Treaty Organization fleets.

[7] Later that year, Siboney was docked at the Norfolk Naval Shipyard for modernization; she returned to active service with the fleet on 20 January 1952.

Siboney passed the following two years participating in routine fleet training exercises that ranged from the coast of New England to the Caribbean.

[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.