In retrospect, it is now clear that there were a few tantalizing warning signs of the impending assault. But U.S. officials and the American personnel assigned to spy on the Japanese and interpret their decoded messages did not take them seriously, did not understand their significance, or failed to inform the proper authorities in time. In January 1941, for example, U.S. ambassador to Japan Joseph Grew heard a rumor about a possible attack on Hawaii. He passed it along to his superiors in Washington, D.C. Apparently, they assumed the information was not reliable and ignored it.

A more ominous piece of information came to light in September 1941 when the navy department intercepted a message sent from Tokyo to the Japanese consulate in Honolulu, Hawaii. The message ordered the chief Japanese official there to report regularly on the number, kinds...