By mid-November 1942 the United States Navy was reduced to two aircraft carriers: Enterprise (90 aircraft) needed repairs and Saratoga (78 aircraft) had put to sea after extensive repairs.
For the Imperial Japanese Navy the light carrier Shoho (a converted seaplane tender like Zuiho; carried 30 planes) was sunk at the tactical victory of the Coral Sea (May 4 to 8) and, more importantly, the fleet carrier Shokaku (72 planes) was heavily damaged. In addition, the fleet carrier Zuikaku (Shokaku class; also carried 72 planes) was removed from action while new air crews were trained. At Midway (June 4 to 7) the Imperial Japanese Navy had lost four fleet carriers: Akagi, Kaga, Soryu and Hiryu. Note that the training carrier Hosho sailed as part of main battle fleet at Midway, as did the light carriers Chiyoda and Nisshin (converted seaplane tenders; 30 aircraft) and Zuiho (converted submarine tender; carried 30 planes). None of those three vessels launched or received aerial attacks.
The light carrier Ryujo (48 planes) was sunk at the battle of the Eastern Solomons on August 24.
That left the Imperial Japanese Navy with
- two converted passenger liners, Junyo and Hiyo (both capable of carrying 48-53 aircraft)
- two converted seaplane tenders (Chiyoda and Nisshin, 30 aircraft each)
- Converted submarine tender Zuiho (30 aircraft)
- three converted cargo liners which were designated escort carriers: Taiyo, Unyo and Chuyo could carry about 30 aircraft each.
- The Imperial Japanese Army had converted two passenger liners to serve as escort carriers – they would probably be described as amphibious assault ships today. The Nigitsu Maru and Akitsu Maru could carry eight planes or ferry 30 planes. Initially, they were not capable of operating Navy warplanes.
So 168 US aircraft on two ships potentially opposed by almost 300 Japanese aircraft on eight to ten ships.
In the pipeline for Japan
- Converted submarine tender Ryuho (31-36 aircraft). She was damaged during the Doolittle Raid (April 18 1942) and not available until November. During a transit to Truk she was torpedoed by submarine USS Drum in December 1942 and was out of action until March 1943.
- The fleet carrier Taiho (60 aircraft) was launched in April 1943 and commissioned on March 7 1944. She was sunk by the submarine USS Albacore at the battle of the Philippine Sea on June 19 1944.
- The fleet carriers Unryu and Amagi were launched in September and October of 1943, respectively. They were commissioned in August 1944.
- The Chitose and Chiyoda were converted seaplane tenders capable of carrying 30 aircraft each that were available in January of 1944. They were both sunk during the Battle of Leyte Gulf on October 25 1944.
- The escort carrier Kaiyo (24 aircraft) was a converted ocean liner that was available in November 1943
- The escort carrier Shinyo (33 aircraft) was a converted (interned) German ocean liner that was commissioned in November 1943 and sunk by submarine USS Spadefish on November 17, 1944.