In March and April 1942, Akagi's aircraft helped sink a British heavy cruiser and an Australian destroyer in the Indian Ocean Raid.

The loss of Akagi and three other IJN carriers at Midway was a crucial strategic defeat for Japan and contributed significantly to the Allies' ultimate victory in the Pacific.

Akagi, the only remaining member of her class, was launched as a carrier on 22 April 1925 and commissioned at Kure Naval Arsenal on 25 March 1927, although trials continued through November 1927.

[16] This heavy gun armament was provided in case she was surprised by enemy cruisers and forced to give battle, but her large and vulnerable flight deck, hangars, and superstructure made her more of a target in any surface action than a fighting warship.

[13] In Akagi's predecessor, Hōshō, the hot exhaust gases vented by swivelling funnels posed a danger to the ship, and wind-tunnel testing had not suggested any solutions.

The larger, forward funnel was angled 30° below horizontal with its mouth facing the sea, and the smaller one exhausted vertically a little past the edge of the flight deck.

[24] Akagi was reduced to second-class reserve status on 1 December 1931 in preparation for a short refit in which her arresting gear was replaced and her radio and ventilation systems were overhauled and improved.

Aerial strikes against enemy carriers were later (beginning around 1932–1933) deemed of equal importance, with the goal of establishing air superiority during the initial stages of battle.

[9] The upper flight deck was extended to the bow, increasing its length to 249.17 meters (817 ft 6 in) and raising aircraft capacity to 86 (61 operational and 25 in storage).

[9][30] The modernization added an island superstructure on the port side of the ship, which was an unusual arrangement; the only other carrier to share this feature was a contemporary, the Hiryū.

[38] 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.

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.

[48] Commanded by Captain Kiichi Hasegawa, Akagi was Vice Admiral Chūichi Nagumo's flagship for the striking force for the attack on Pearl Harbor[39] that attempted to cripple the United States Pacific Fleet.

In the second wave, 18 Aichi D3A "Val" dive bombers from the carrier targeted the battleships Maryland and Pennsylvania, the light cruiser Raleigh, the destroyer Shaw, and the fleet oiler Neosho while nine "Zeros" attacked various American airfields.

One of the carrier's Zero fighters attacked a Boeing B-17 Flying Fortress heavy bomber that had just arrived from the mainland, setting it on fire as it landed at Hickam, killing one of its crew.

[50] In January 1942, together with the rest of the First and Fifth Carrier Divisions, Akagi supported the invasion of Rabaul in the Bismarck Archipelago, as the Japanese moved to secure their southern defensive perimeter against attacks from Australia.

[52] Akagi, along with Kaga and the carrier Zuikaku, sortied in search of American naval forces raiding the Marshall Islands on 1 February 1942, before being recalled.

Later that same day the American destroyer Edsall was attacked and sunk by D3As from Akagi and Sōryū, in combination with gunfire from two battleships and two heavy cruisers of the escort force.

Akagi and her consorts covered the invasion of Java, although her main contribution appears to have been providing 18 B5Ns and 9 Zeros for the 5 March air strike on Tjilatjap.

On 9 April, she attacked Trincomalee with 18 B5Ns, escorted by 6 Zeros which claimed to have shot down 5 Hawker Hurricane fighters (only two of which can be confirmed from Allied records) without loss to themselves.

Meanwhile, a floatplane from the battleship Haruna spotted the small aircraft carrier Hermes, escorted by the Australian destroyer Vampire, and every available D3A was launched to attack the ships.

Akagi contributed 17 dive bombers and they helped to sink both ships; they also spotted the oil tanker RFA Athelstone, escorted by the corvette Hollyhock, and sank both without loss.

[56] On 19 April 1942, while near Taiwan during the transit to Japan, Akagi, Sōryū, and Hiryū were sent in pursuit of the American carriers Hornet and Enterprise, which had launched the Doolittle Raid.

The aircraft, either attempting a suicide ramming, or out of control, narrowly missed striking the carrier's bridge, which could have killed Nagumo and his staff, and crashed into the ocean.

[68] This experience may well have contributed to Nagumo's determination to launch another attack on Midway, in direct violation of Yamamoto's order to keep the reserve strike force armed for anti-ship operations.

The high altitude of the bombers gave the Japanese captains enough time to anticipate where the bombs would land and successfully maneuver their ships out of the impact area.

At the last minute, one of McClusky's elements of three bombers from VB-6, led by squadron commander Richard Best who deduced Kaga to be fatally damaged, broke off and dove simultaneously on Akagi.

This hit set off explosions among the fully armed and fueled B5N torpedo bombers that were being prepared for an air strike against the American carriers, resulting in an uncontrollable fire.

Whether the system functioned or not is unclear, but the burning aviation fuel proved impossible to control, and serious fires began to advance deeper into the interior of the ship.

Rob Kraft and Naval History and Heritage Command historian Frank Thompson aboard RV Petrel identified the wreck of Akagi using high-frequency sonar.