I first wrote about this back in 2007,
From the Library of Congress:
On December 7, 1941, Japanese planes attacked the United States Naval Base at Pearl Harbor, Hawaii Territory killing more than 2,300 Americans. The U.S.S. Arizona was completely destroyed and the U.S.S. Oklahoma capsized. The attack sank three other ships and damaged many additional vessels. More than 180 aircraft were destroyed.
A hurried dispatch from the ranking United States naval officer in Pearl Harbor, Commander in Chief Pacific, to all major navy commands and fleet units provided the first official word of the attack at the ill-prepared Pearl Harbor base. It said simply: AIR RAID ON PEARL HARBOR X THIS IS NOT DRILL.