War with Japan appeared imminent, and on Dec. 1, the Japanese navy suddenly changed the radio call signs of its ships. This shift was ominous because the Communications Intelligence Unit at Pearl Harbor plotted the position of the Japanese fleet by intercepting these signals. Traffic analysts quickly identified the most commonly used new calls but were unable to locate a single Japanese aircraft carrier. Worse, none had been picked up since Nov. 25. Five days later, a Japanese task forced approached undetected to within 230 miles of Hawaii and struck a devastating blow on the naval base at Pearl Harbor and nearby air bases. Surprise was complete. "Pearl Harbor was still asleep in the morning mist," one of the Japanese pilots later reported. "It was calm and serene inside the harbor, not even a trace of smoke arising from the ships . . ."
Nineteen vessels, including the entire battle line of the Pacific Fleet. were sunk or badly damaged in the worst disaster in American military history. More than 2,400 sailors, soldiers and Marines were killed -- nearly half in the explosion of the battleship Arizona. Neatly lined up as for inspection, an estimated 256 aircraft were destroyed.
