Answer:
The US radar men reported a group of incoming aircraft to their superiors prior to the attack on Pearl Harbor on December 7, 1941. The radar operators believed the incoming planes were Japanese, but their superiors did not take immediate action to investigate or respond to the potential threat. As a result, the attack on Pearl Harbor caught the US military by surprise and caused significant damage and loss of life. The failure to act on the radar men's report has since been criticized as a critical mistake in the US military's handling of the situation.