Dec. 8 (Japan time) is the 72nd anniversary of Pearl Harbor, the infamous attack launched by Imperial Japanese forces against the United States that continues to reverberate in the popular imagination.

Certainly, the 2,402 deaths made this raid unforgettable. So too the sunken and savaged U.S. Navy vessels that lay smoldering after the attack. But the reason President Franklin D. Roosevelt declared it a Day of Infamy was the nature of the attack.

Japan gave no public warning, had not cut diplomatic ties or declared war by the time it opened hostilities with its Pearl Harbor attack in 1941. The strike was planned to be a surprise, and indeed that was a crucial element in its fleeting success.