In 1941 CE, it was attacked, by surprise, by the Empire of Japan, bringing the United States into what was called World War II. As the attacking planes approached, they were spotted by a radar crew, but the officer they called decided it was an expected friendly flight, and told them "not to worry about it".
Honor Harrington considered the Japanese attack on Pearl Harbor the first instance in which long range sensor readings were misread due to prior expectations, resulting in essentially complete surprise when the aircraft in question turned out to be an enemy attack force. (HH8)
- Detailed article about the Pearl Harbor attack on Wikipedia