Operation I-Go

Operation I-Go (い号作戦, I-Go sakusen) was an aerial counter-offensive launched by Imperial Japanese forces against Allied forces during the Solomon Islands and New Guinea Campaigns in the Pacific Theater of World War II from 1–16 April 1943. In the operation, Japanese aircraft—primarily from Imperial Japanese Navy units under the command of Admirals Isoroku Yamamoto and Jinichi Kusaka—attacked Allied ships, aircraft, and land installations in the southeast Solomon Islands and New Guinea. The goal of the operation was to halt the Allied offensives in New Guinea and the Solomons and to give Japan time to prepare a new set of defenses in response to recent defeats to the Allies in the Battle of Guadalcanal and in New Guinea at Buna–Gona, Wau, and the Bismarck Sea.

Operation I-Go
Part of the Pacific Theater of World War II

Isoroku Yamamoto (far left) and Jinichi Kusaka (center left) supervise air operations from Rabaul during Operation I-Go in April 1943
Date1–19 April 1943
Result Inconclusive
Allied forces including:
 United States
 New Zealand
Commanders and leaders
William Halsey, Jr
Douglas MacArthur
Isoroku Yamamoto
Jinichi Kusaka
350 aircraft
Casualties and losses
1 destroyer,
1 tanker,
2 transports,
1 corvette sunk,
25 aircraft destroyed[1]
55 aircraft destroyed[2]

The operation consisted of several massed aerial attacks by Japanese bomber and fighter aircraft—based at Rabaul, Bougainville, and the Shortland Islands—against Allied targets on and around Guadalcanal and the Russell Islands in the Solomons and Port Moresby, Oro Bay, and Milne Bay in New Guinea. Although the Japanese sank several Allied transports and warships, the attack failed to inflict serious damage on Allied forces. Based on inaccurate and unintentionally exaggerated reports from the involved aircrews, Yamamoto halted the attacks on 16 April, believing the operation to be a success. The operation, however, did not significantly delay Allied preparations for further offensives in the South Pacific area. Yamamoto was killed shortly thereafter while traveling to congratulate units that had participated in the operation.

Air attacks

On 1 April 1943 a fighter sweep of 58 Mitsubishi A6M3 Zeros of the 204th, 251st and 582st Kōkūtai was met by Allied fighters over the Russell Islands intercepting the Japanese en route to Tulagi and Guadalcanal, that claimed 18 Zeros at the cost of six Allied aircraft.

The next attack was launched on 7 April, a raid by 67 Aichi D3A2 "Val" dive bombers escorted by 110 Zeros against Guadalcanal and was met by 76 Allied fighters. Twenty-one Japanese aircraft were lost; the Allies lost seven. The raid resulted in the sinking of the destroyer USS Aaron Ward, the corvette HMNZS Moa, and the tanker USS Kanawha.

On 11 April, a force of 22 "Vals" and 72 Zeros attacked shipping at Oro Bay, near Buna. 50 Allied fighters scrambled from Dobodura and intercepted the force, shooting down six Japanese aircraft without loss.

An attack on Port Moresby on 12 April by a force of 131 Zeros—of the 253rd Kōkūtai and air groups of the carriers Zuikaku and Zuihō and 43 Mitsubishi G4M2 "Betty" medium bombers of the 751st and 705th Kōkūtai struck Port Moresby. Opposed by 44 Allied fighters, the attack resulted in two Allied and five Japanese aircraft lost. The raid damaged a few small craft and damaged or destroyed additional Allied aircraft on Port Moresby airfields.

On 14 April 1943, the Japanese launched an attack against Milne Bay with 188 aircraft. Twenty-four Curtiss Kittyhawk Mk 1As intercepted the attacking force, resulting in seven Japanese and three Allied aircraft shot down. The Dutch cargo ship Van Heemskerk was beached after being hit by several bombs, which set it ablaze. The British cargo ship Gorgon was also bombed and set on fire, before the blaze was extinguished. Near misses damaged the Dutch cargo ship Van Outhoorn and the Australian minesweepers HMAS Wagga and Kapunda. Four Allied servicemen and 12 merchant seamen were killed in the air raid, with 68 injured.


  1. Morison, pp. 117–127.
  2. Gamble, pp. 316–331.



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