Operation Vengeance was the American military operation to kill Admiral Isoroku Yamamoto of the Imperial Japanese Navy on April 18, 1943, during the Solomon Islands campaign in the Pacific Theater of World War II. Yamamoto, commander of the Combined Fleet of the Imperial Japanese Navy, was killed on Bougainville Island when his transport bomber aircraft was shot down by United States Army Air Forces fighter aircraft operating from Kukum Field on Guadalcanal. The mission of the U.S. aircraft was specifically to kill Yamamoto and was based on United States Navy intelligence on Yamamoto's itinerary in the Solomon Islands area. The death of Yamamoto reportedly damaged the morale of Japanese naval personnel, raised the morale of the Allied forces, and was intended as revenge by U.S. leaders, who blamed Yamamoto for the attack on Pearl Harbor that initiated the war between Imperial Japan and the United States. The U.S. pilots claimed to have shot down three twin-engine bombers and two fighters during the mission, but Japanese records show only two bombers were shot down. There is a controversy over which pilot shot down Yamamoto's plane, but most modern historians credit Rex T. Barber. Background Admiral Isoroku Yamamoto, commander of the Imperial Japanese Navy, scheduled an inspection tour of the Solomon Islands and New Guinea. He planned to inspect Japanese air units participating in Operation I-Go that had begun April 7, 1943; in addition, the tour would boost Japanese morale following the disastrous Guadalcanal Campaign and its subsequent evacuation during January and February. Intelligence On April 14, the U.S. naval intelligence effort code-named "Magic" intercepted and decrypted orders alerting affected Japanese units of the tour. The original message, NTF131755, addressed to the commanders of Base Unit No. 1, the 11th Air Flotilla, and the 26th Air Flotilla, was encoded in the Japanese Naval Cipher JN-25D, and was picked up by three stations of the "Magic" apparatus, including Fleet Radio Unit Pacific Fleet. The message was then deciphered by Navy cryptographers (among them future Supreme Court Justice John Paul Stevens); it contained time and location details of Yamamoto's itinerary, as well as the number and types of planes that would transport and accompany him on the journey. The decrypted text revealed that on April 18 Yamamoto would fly from Rabaul to Balalae Airfield, on an island near Bougainville in the Solomon Islands. He and his staff would fly in two medium bombers (Mitsubishi