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).

[2] The keel for the ship, originally named Saltery Bay, was laid down on 5 June 1944 at the Todd-Pacific Shipyards in Tacoma, Washington.

Saidor conducted her initial training and shakedown cruise off the West Coast of the United States, and then operated out of Pearl Harbor from 12 December to 20 March 1946.

[6] Ten of the Commencement Bay-class ships saw significant service postwar as anti-submarine warfare (ASW) carriers, but they were small and had difficulty operating the new Grumman AF Guardian patrol planes, so the rest of the class remained laid up, and they were soon replaced in the ASW role by much larger Essex-class aircraft carriers.