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Naval History and Heritage Command

National Museum of the U.S. Navy

Japanese "I" Operation:  April 1-19, 1943

Due to the Japanese defeats at Guadalcanal, New Guinea, and the numerous ship losses at Bismarck Sea, Admiral Isoroku Yamamoto began to gather aircraft in early April for an aerial counter-offensive named "I" Operation to halt the American offensive.   As the Japanese gathered their forces, U.S. reconnaissance and intelligence became aware of the impending offensive.   On April 7, enemy air attacks successfully hit and sank USS Aaron Ward (DD-483) and New Zealand corvette HMNZS Moa, with numerous other support ships also being damaged, such as USS Kanawha (AO-1), which would sink the following day.   Though the Japanese were successful in some of their attacks, the lack of experienced aviators worked against them.  As the campaign progressed, and with the U.S. learning that Yamamoto would visit Japanese bases in the area, it became apparent that the Admiral had to be eliminated.   On April 18, while traveling in a Mitsubishi G4M "Betty" aircraft, Yamamoto was shot down by U.S. Army Air Force P-38 aircraft, in a team led by Major John W. Mitchell, USA.  The Admiral's loss dealt a blow to the morale of the Japanese forces. 

Image:  NH 97810:  Japanese "I" Operation, April 1943.  Ships of Task Force 18 in Tulagi Harbor, shortly before departing to avoid the large-scale Japanese air attack on April 7, ,1943.  U.S. Navy Photograph, now in the collections of the National Archives.