On 7 December 1941, a massive strike of 183 aircraft roared off six Japanese carriers to strike Pearl Harbor. Sixteen torpedo bombers were to attack U.S. aircraft carriers moored on the northwest side of Ford Island. If there were no carriers in port (as would be the case), they were to look for alternate targets.
One order was stressed: Do not waste a torpedo on the USS Utah (formerly BB-31, then AG-16).
The Utah was a demilitarized battleship converted into an antiaircraft gunnery training platform. She often rested at the carrier moorings, and the Japanese knew it. The torpedo bomber air crews were drilled intensively to recognize her silhouette.