TheCodeBreakers
He fired a "black dragon" from his signal pistol to indicate that the
squadrons should deploy in the assault pattern for complete surprise.
Nine minutes later, he wirelessed the message "To, to, to"—the first
syllable of the Japanese word for "Charge!" and the signal to attack. As
the planes moved into position for their runs, he felt so certain that he
had achieved complete surprise that, at 7:53, two minutes before the
first bomb even fell, he jubilantly radioed "TORA! TORA! TORA!" ("Tiger! Tiger!
Tiger!")—the prearranged codeword that indicated surprise. On Akagi,
Nagumo turned to a brother officer and grasped his hand in a long, silent
handshake. At 7:55, the first bomb exploded at the foot of the seaplane
ramp at the southern end of Ford Island in the middle of Pearl Harbor.
Okumura was still typing. His fingers struggled with the keys as
torpedoes capsized Oklahoma, as bombs sank West Virginia, as 1,000
annaabi.ee 
