USS Illinois

USS Illinois (CV-12) was a Unique United States Aircraft, built from the converted hull of a Iowa-class Battleship. Originally laid down in 1942 as USS Illinois BB-66, work was paused on her in 1942 to focus on aircraft carrier and Montana-class battleship production. After the losses at Midway, she was reordered to be completed as an aircraft carrier.

Upon completion in March 1944, due to an expanded torpedo protection system, she became the first US warship to be completed unable to fit through the Panama Canal locks, requiring her to sail around the tip of South America. She would serve in front line service in the South Pacific Threater until late 1946, when she was reclassified as an auxillary aircraft carrier.

Decommisioned on March 18, 1951, she was entered into the mothball fleet and scrapped 1965.

## Background & Construction

BB-65 was originally authorized to be the hull number for the first Montana-class battleship. However, the looming threat of war and need for industrial mobilization led the US Navy reordering BB-65 and BB-66 as modified Iowa-class battleships USS Illinois and USS Kentucky. The USS Illinois and Kentucky were the first battleships to be laid down without any restriction from the Washington Naval Treaty. While some changes had been made to her sisterships USS Missouri and USS Wisconsin, primarily the inclusion of thicker bulkheads, they were ultimately too far along in their construction for major changes. The new Illinois-subclass however would be free of these restrictions.

Laid down in early 1941, she was 22% completed when work was slowed in early 1942 favor of prioritizing Montana-class battleships and Essex-class aircraft carriers. The discovery of Japanese work on the 20.1in armed Aki-class and 18.1in armed German Tegetthoff-class rendered the Illinois and Kentucky obsolete, and work was officially postponed.

   However, after the devastating early war losses of American aircraft carriers, the US Navy ordered that the incomplete USS Illinois to be completed as an aircraft carrier with emergency priority given to her construction. Since Kentucky was to far along in her construction to be easily converted, equipment for the Kentucky was diverted to the Illinois.

The USS Illinois would incorporate features from the under-construction Essex-class, aswell as lessons learned from early war experience.

## Design

At the time of work being paused on her in 1942, USS Illinois was only 22% complete. Due to her relatively incomplete nature at the time of her conversion, many modifications were made to her hull to best adapt her to Aircraft Carrier duty. The USS Illinois was influenced by the development of the Essex-class Aircraft Carriers, as well as lessons learned from the conversion process of the Independence-class aircraft carriers.

Most modifications made to the hull of Illinois centered around improving her survivability. The USS Illinois became the first US carrier to not fit in the Panama Canal locks after her torpedo blisters were enlarged, increasing her beam to 117ft 4in. Additionally, enlarged 17.5in bulkheads were fitted. Due to the slender bow of the Iowa-class, the USS Illinois marked a departure from an open bow as seen on Yorktown-class and Essex-class carriers, and returned to an enclosed hurricane bow seen on the Constitution-class to improve seakeeping in heavy seas.

However, her island design and armament layout was more or less copied from the Essex-class with minimal changes made.