Most people who know about Pearl Harbor, the battle that brought America fully into World War II, believe that the Japanese attack was completely without warning. The common misconception is that the first indication of attack occurred when Japanese bombs starting raining from the skies.
But before the planes of the Japanese arrived, their midget submarines were attempting to penetrate Pearl Harbor. One of these subs was spotted by a patrolling American warship.
On the morning of December 7, 1941, the U.S.S. Ward was conducting a precautionary patrol off the entrance to Pearl Harbor when crewmen spotted the submarine. The Japanese were attempting to sneak through the submarine nets into the harbor in the wake of another American vessel. A submarine inside the harbor could inflict horrendous damage, firing point blank into the moored battleships.