The attack on Pearl Harbor began just before 8 AM, as fighter pilot Mitsuo Fuchida shouted “Tora, Tora, Tora!” The word means “tiger,” but it was also a radio code acronym meaning “lightning attack,” signalling the attack was a total surprise to everyone at the naval base. Fighter planes, bombers, and torpedoes were used, with the attack intended to prevent the US Pacific Fleet from interfering with Japanese plans in Southeast Asia. Within hours after the Pearl Harbor attack, the Japanese had also hit the Philippines, Guam, Wake Island, Malaya, Singapore, and Hong Kong.
Striking the Pacific Fleet at anchor in Pearl Harbor carried two distinct disadvantages: the targeted ships would be in very shallow water, so it would be relatively easy to salvage and possibly repair them; and most of the crews would survive the attack, since many would be on shore leave or would be rescued from the harbor. A further important disadvantage—this of timing, and known to the Japanese—was the absence from Pearl Harbor of all three of the . Pacific Fleet's aircraft carriers ( Enterprise , Lexington , and Saratoga ). IJN top command was so imbued with Admiral Mahan 's " Decisive battle " doctrine—especially that of destroying the maximum number of battleships—that, despite these concerns, Yamamoto decided to press ahead.  [ page needed ]