(Grace) Hallenbeck (mother of Major Pappy Boyington, then a Prisoner of War of the Japanese), and commissioned as Block Island on 30 December 1944.

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.

[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).

The flight leader attempted to land his Avenger first at San Nicolas, then at Santa Barbara, and ultimately at Bakersfield, but he also crashed before reaching the airfield, killing the three-man crew.

The incident forced the cancellation of training, as Block Island and Childs spent the next day searching for downed pilots before returning to San Diego.

[6] Block Island thereafter resumed an intensive training schedule for the next month in preparation for deployment to the western Pacific to join the forces fighting Japan.

Block Island's anti-aircraft gunners accidentally opened fire on two American planes, but did not shoot them down before realizing they were friendly aircraft.

Block Island joined Task Unit 52.1.1, commanded by Rear Admiral Calvin Durgin, on 3 May some 64 nautical miles (119 km; 74 mi) southeast of Okinawa.

Japanese defensive fire shot down two of the TBMs, though one of them managed to limp back to the carrier and ditch nearby, allowing its crew to be picked up by an escorting destroyer.

On the 27th, a sweep by four fighters over Ishigaki resulted in the death of VMF-511's commander after his aircraft failed to pull out of a dive during a rocket attack on the harbor facilities there.

[6] On 19 June, Block Island arrived in Leyte Gulf in the northern Philippines for a brief period of rest before sortieing as part of the invasion fleet for what was to be the last major amphibious assault of the Pacific War.

Block Island lay at Leyte from 17 to 28 August, when she departed as part of Task Group 77.1, which also included Santee and four destroyer escorts.

The ships sailed on 29 August and encountered a typhoon on the way; the storm lasted from 1 to 3 September, but the task groups avoided damage by staying to the south, near Formosa.

Block Island sent a group of 33 marines and a medical team aboard the destroyer escorts Thomas J. Gary and Kretchmer to Keelung.

Later that morning, Ketcham sent a TBM Avenger from Block Island to land at Matsuyama and make direct contact with the local commander.

Marine Major Peter Folger ordered the commander to take him to the local camps so he could evaluate the situation and coordinate the relief effort.

Aircraft carrying medicine and food were soon sent to Matsuyama, with orders conveyed between Folger and Block Island by one of her Hellcats, which orbited over the camps to relay radio messages.

The planes flew in some 9,000 lb (4,100 kg) of supplies and the marine colonel who arrived with the landing party commandeered a train to carry the more than 1,000 POWs from the camps back to Keelung.

While en route, they met a British carrier task force that replaced them off Formosa to patrol over the camps, as there were still men who had to be left behind, as they were judged to be too sick for the voyage.

[6] On 5 January 1946, Block Island left San Diego for the last time, bound for the East Coast of the United States by way of the Panama Canal.

For the next few months, she made cruises north to New York City and south to Guantanamo Bay, Cuba, after which she served as a training ship for naval recruits off the coast of Virginia.

[6] Following the outbreak of the Korean War in mid-1950, the Navy badly needed operational warships, and so Block Island's career as a cadet training ship came to an end on 3 October 1950, when she was transferred to the Atlantic Reserve Fleet.

[6] On 5 January 1953, Block Island departed Hampton Roads, Virginia, bound for another training cruise to the West Indies that lasted more than a month.

[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.

The program represented the culmination of Marine Corps tests through the late 1940s and 1950s using helicopters as a component of their "vertical assault" doctrine, which envisioned using helicopter-borne troops to seize strategic crossroads behind the lines while traditional amphibious forces went ashore.

Work on Block Island began in January 1958, but by this time, the remaining Essex-class carriers that had not been converted to SCB-27 configuration had become available for use as amphibious assault ships.