Japanese Aircraft Carrier Akagi - Lead-up To World War II

Lead-up To World War II

Akagi's modernization was completed on 31 August 1938. She was reclassified as a first reserve ship on 15 November, but did not rejoin the First Carrier Division until the following month. In her new configuration, the carrier embarked 12 Mitsubishi A5M "Claude" fighters with 4 disassembled spares, 19 Aichi D1A dive bombers with 5 spares, and 35 Yokosuka B4Y horizontal/torpedo bombers with 16 spares. She sailed for southern Chinese waters on 30 January 1939 and supported ground operations there, including attacks on Guilin and Liuzhou, until 19 February, when she returned to Japan. Akagi supported operations in central China between 27 March and 2 April 1940. She was reclassified as a special purpose ship (Tokubetse Ilomokan) on 15 November 1940, while she was being overhauled.

The Japanese experiences off China had helped further develop the IJN's carrier doctrine. One lesson learned in China was the importance of concentration and mass in projecting naval air power ashore. Therefore, in April 1941, the IJN formed the First Air Fleet, or Kido Butai, to combine all of its fleet carriers under a single command. On 10 April 1941 Akagi and Kaga were assigned to the First Carrier Division as part of the new carrier fleet, which also included the Second (with carriers Hiryū and Sōryū), and Fifth (with Shōkaku and Zuikaku) carrier divisions. The IJN centered its doctrine on air strikes that combined the air groups of entire carrier divisions, rather than individual carriers. When multiple carrier divisions were operating together, the divisions' air groups were combined. This doctrine of combined, massed, carrier-based air attack groups was the most advanced of its kind in the world. The IJN, however, remained concerned that concentrating all of its carriers together would render them vulnerable to being wiped out all at once by a massive enemy air or surface strike. Thus, the IJN developed a compromise solution in which the fleet carriers would operate closely together within their carrier divisions but the divisions themselves would operate in loose rectangular formations, with approximately 7,000 meters (7,700 yd) separating each carrier.

The Japanese doctrine held that entire carrier air groups should not be launched in a single massed attack. Instead, each carrier would launch a "deckload strike" of all its aircraft that could be spotted at one time on each flight deck. Subsequent attack waves consisted of the next deckload of aircraft. Thus, First Air Fleet air attacks would often consist of at least two massed waves of aircraft. The First Air Fleet was not considered to be the IJN's primary strategic striking force. The IJN still considered the First Air Fleet an integral component in the Combined Fleet's Kantai Kessen or "decisive battle" task force centered on battleships. Akagi was designated as the flagship for the First Air Fleet, a role the ship retained until her sinking 14 months later.

Although the concentration of so many fleet carriers into a single unit was a new and revolutionary offensive strategic concept, the First Air Fleet suffered from several defensive deficiencies that gave it, in Mark Peattie's words, a "'glass jaw': it could throw a punch but couldn't take one." Japanese carrier anti-aircraft guns and associated fire-control systems had several design and configuration deficiencies that limited their effectiveness. Also, the IJN's fleet combat air patrol (CAP) consisted of too few fighter aircraft and was hampered by an inadequate early warning system, including lack of radar. In addition, poor radio communications with the fighter aircraft inhibited effective command and control of the CAP. Furthermore, the carriers' escorting warships were not trained or deployed to provide close anti-aircraft support. These deficiencies, combined with the shipboard weaknesses previously detailed, would eventually doom Akagi and other First Air Fleet carriers.