The Real Reason Why Imperial Japan Did Not Build More Aircraft Carriers in World War II

By Unknown - 広島県呉市海事歴史科学館所蔵品。Kure Maritime Museum, Japanese Naval Warship Photo Album: Aircraft carrier and Seaplane carrier, Supervisory editor: Kazushige Todaka, p. 12., Public Domain, https://commons.wikimedia.org/w/index.php?curid=3558447
September 7, 2019 Topic: History Region: Asia Blog Brand: The Buzz Tags: World War IIImperial JapanUS NavyCarriersMilitary History

The Real Reason Why Imperial Japan Did Not Build More Aircraft Carriers in World War II

They couldn't. 

Considering these six specific carriers and not counting other Essex-class carriers under construction, the Japanese built 25.2 tons of Unryu-class carriers per day, and the United States built 52.1 tons of Essex-class carriers per day. U.S. shipyards built twice as much tonnage each day and delivered each ship 24 percent faster. The United States sustained similar construction efforts over the course of the war, whereas Japan did not.

 

So, from mid-1942 to early 1944, Japan could bring into service only three fleet carriers, Junyo, Hiyo,and Taiho, all laid down before war began, the first two of which were conversions from ocean liners rather than purpose-built. Shipyards laid down or converted more carriers, launched them, and commissioned them during the war. For example, the light carriers Chitose and Chiyoda were converted from seaplane carriers, but all too late. Japan built no light or escort carriers from the keel up during the war.

Troubles with Training

There is more to building an aircraft carrier than shipbuilding. Early in 1943, the military realized it had to drastically expand pilot training to a level three times the current structure. The Japanese wanted to do three things: increase the numbers of replacements going to units engaged in combat, build up the training base, and accumulate a reserve of pilots for future operations.

The Navy increased its training air groups from 15 to 48. The first part of the pilot requirement came from the optimistic need to man up to six Taiho-class carriers, up to 16 and later 14 Unryu-class carriers, carrier conversion Shinano, up to four hermaphrodite battleship conversions, one cruiser conversion to a light carrier (Ibuki), the conversion of heavy cruiser Mogami into an aircraft cruiser, and the light carrier conversions Chitose and Chiyoda. There were also three 1943 escort carrier conversions planned, Kaiyo and Shinyo, both completed, and Brazil Maru, sunk before conversion. The Japanese actually used their escort carriers most frequently as aircraft transports, so those ships did not often need pilots.

A second part of the pilot requirement came from plans to activate the First Air Fleet of over 1,600 authorized aircraft with two air flotillas, the 61st and the 62nd. A third part of the requirement came from simply maintaining the current strength of land- and carrier-based air groups as well as pilots for seaplane carriers and light and heavy cruisers. In mid-1942, the pilot training program might have looked achievable. No new fleet carriers were expected to come on line until 1944 with Taiho. But no one had foreseen the severity of pilot losses soon to come.

Most of these training air groups operated from 52 bases in Japan, while two bases were in the Philippines, five bases on Formosa, and five bases in the Singapore area. The critical bottleneck in training pilots and crewmen was inadequate training equipment. Training bases had low priority for the issuing of Japan’s limited number of aircraft.

Training aircraft were in short supply and often of poor quality. Any delays or shortfalls in aircraft production seriously affected training units. The Japanese increased fighter production 171 percent from 1941 to 1942 and 143 percent from 1942 to 1943. They increased bomber production by 66 percent and 72 percent during those same two years. The production of trainers, however, increased only 46 percent in 1942 and 32 percent in 1943. The Japanese had established their production priorities, and trainers were well down the list.

Instructors had too many students to manage them effectively. The urgency to train pilots overwhelmed the curriculum. Veteran naval ace Saburo Sakai recalled in early 1943, “We couldn’t watch for individual errors and take the long hours necessary to weed the faults out of a trainee.” The decision to press for quantity over quality meant that poorly trained fliers graduated to combat units. “We were told to rush men through, to forget the fine points, just teach them how to fly and shoot.”

Thus, aside from the problems of actually building aircraft carriers in the numbers projected, the Japanese could never have built escorts or trained enough fliers, mechanics, and armorers to operate with them. The last gasp of naval air power afloat occurred in June 1944, at the Battle of the Philippine Sea, before the first of the Unryu-class carriers was commissioned.

Production Grinds to a Halt

The Japanese war effort was so unbalanced and so crippled by industrial and managerial weaknesses that the June 30, 1942, aircraft carrier plan was little more than a feverish reaction to Coral Sea and Midway. The fever would ultimately break. The five-Taiho program was cancelled. The 14-Unryu program ground to a halt after six hulls had been laid and launched, three ships commissioned, and one of those three deployed as a transport.

John W. Whitman is the author of Bataan: Our Last Ditch—The Bataan Campaign, 1942. He is a retired U.S. Army lieutenant colonel and a holder of the Combat Infantryman’s Badge. He resides in Alexandria, Virginia.

Originally Published in 2016.

This article by John W. Whitman originally appeared on the Warfare History Network.

Image: Wikimedia Commons