After the retreat from Guadalcanal, Japanese commander Admiral Yamamoto -- the chief architect of the attack on Pearl Harbor -- sought to shore up his defenses. He staged a massive series of air strikes at Guadalcanal and New Guinea. Yamamoto mistakingly believed these raids to be successful. However, in early April 1943, U.S. intelligence intercepted information regarding Yamamoto's itinerary. On April 18, a squadron of P-38s intercepted Yamamoto's plane in the South Pacific. In additional to losing their greatest military strategist, Japanese morale suffered terribly when the announcement was finally made in May.