"It just wasn't in their frame of reference," says naval historian Lawrence H. Suid.
Today, a number of what-ifs, or enduring mysteries, about the Pearl Harbor attack continue to inspire debate. Among them:
Why didn't the US see Japanese planes coming on radar? Actually, US Army radar operators did spot the Japanese air assault on radar. They just did not know what they were seeing.
Radar technology was in its infancy, and an Army crew was training on a new radar installed at the northern point of the Hawaiian island of Oahu. On Dec. 7, 1941, this crew spotted a mass of incoming somethings larger than they had ever seen. They decided it was probably some expected US B-17s and reported it as such.
But the radar return looked much different from what they were used to seeing.
"Why didn't this stir up their curiosity?" Suid says.
Why did the US Navy ignore the sinking of a Japanese submarine prior to the attack? At 6:37 on the morning of Dec. 7, the USS Ward, an old four-stack destroyer, attacked and destroyed a Japanese mini-sub making its way toward Pearl Harbor.
Crew members of the Ward saw a submarine periscope, dropped depth charges, and saw an oil slick and debris indicating they had destroyed a target. They immediately sent a dispatch saying that they had destroyed "a submarine operating in defense sea areas," according to a copy of the ship's report of the attack.
This incident took place an hour prior to the arrival of the first wave of Japanese warplanes. But US military officials did not heed the warning provided by the Ward, or did not believe it, or simply were unable to react in time.