7 Dec...

Attack on Pearl Harbor
The attack on Pearl Harbor (or Hawaii Operation, Operation Z, as it was called by the Japanese Imperial General Headquarters) was an unannounced military strike conducted by the Japanese navy against the United States naval base at Pearl Harbor, Hawaii on the morning of December 7, 1941. It resulted in the United States entry into World War II. The attack was intended as a preventive action to keep the U.S. Pacific Fleet from influencing the war the Empire of Japan was planning in Southeast Asia against Britain and the Netherlands, as well as the U.S. in the Philippines.
[Wikipedia entry]

Note: "The attack was intended as a preventive action to keep the U.S. Pacific Fleet from influencing the war the Empire of Japan was planning in Southeast Asia..."

Pre-emptive strikes don't seem to work all that well!
Would that we would learn this lesson.