One lesson learned in China was the importance of force concentration and mass in projecting naval air power ashore.

This doctrine of combined, massed, carrier air attack groups was the most advanced of its kind of all the world's navies.

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.

"[2] Japanese carrier anti-aircraft guns and associated fire control systems had several design and configuration deficiencies which limited their effectiveness.

The IJN's fleet combat air patrol (CAP) consisted of too few fighter aircraft and was hampered by an inadequate early warning system, including a lack of radar.

Fourth Kōkū Sentai consisted solely of light carrier Ryūjō and her aircraft unit, until two destroyers were added in August.

When formed on 10 April 1941, First Air Fleet was a naval battlegroup with the single most powerful concentration of carrier-based aircraft in the world at the time.

[6] Military historian Gordon Prange called it "a revolutionary and potentially formidable instrument of sea power.

"[7] Fifth Kōkū Sentai (5th Carrier Division) was created on 1 September 1941 and was added to First Air Fleet The Naval Data Base:航空戦隊..

When the new aircraft carrier Zuikaku was added to Fifth Kōkū Sentai, First Air Fleet consisted of Akagi, Kaga, Sōryū, Hiryū, Ryūjō, Kasuga Maru (renamed Taiyō ca.

It was the single most powerful naval fleet until four of the six aircraft carriers of the unit were destroyed in the disastrous Battle of Midway.

On 30 September 1943, a cabinet meeting planned the Absolute National Defense Zone (絶対国防圏, Zettai Kokubōken) strategy.

The 1st Air Fleet dispatched the Fifth Carrier Division in the Coral Sea during the return from the Indian Ocean.

After this loss of air cover, the Port Moresby invasion force abandoned its mission and retreated north.

USN aircraft managed to damage Shōkaku, meaning that she and her sister ship were unable to participate in the following operation.

Admiral Isoroku Yamamoto planned to lure and destroy USN carriers by attacking the Midway Islands in June 1942.

Carrier Hiryū managed to survive the attack and Rear Admiral Tamon Yamaguchi launched a strike against Yorktown.

[30] Its Number 261 Kaigun Kōkūtai (fighter) advanced to Saipan circa 19–24 February 1944, but attrition in air combats and illness weakened the unit greatly and it played only a minor role in the Battle of the Philippine Sea.

263 Kaigun Kōkūtai (fighter) of the 61st Air Flotilla were stationed on Guam from 15 June 1944 and participated in the battle.

[32] After disastrous losses at the Battle of the Philippine Sea, the Japanese carrier force was again practically without aircrew and aircraft.