As World War Two rages, a simmering conflict emerges between the United States and the Japanese Empire -- though not outright war. Admiral Yamamoto (Sô Yamamura) has a unique plan which will make maximum use of surprise and the superior Japanese Naval Air Arm. He will send most of the Japanese aircraft carriers to the Hawaiian Islands, attacking Pearl Harbor (Oahu) the main American base in the Pacific. After sinking America's Pacific Fleet, especially the Aircraft Carriers, the Japanese Navy will be free to overrun the entire Pacific region. America will have to sue for peace on Japan's terms, surrendering the Far East to their Empire.
As diplomatic relations between the two countries worsen, the American War Department half-heartedly prepares for such a strike. Two American intelligence officers notice unusual traffic between the Japanese Home Islands and their embassy in Washington. Unfortunately for the Americans, higher-ups are in denial, and commanders in Hawaii are more worried about Japanese-American saboteurs than a Naval Air attack. Intelligence estimates state that the Japanese are fully capable of attacking, and would do so on a Sunday morning, but the exact Sunday is unclear.
Admiral Nagumo (Eijiro Tono) skillfully guides his carrier fleet to within a couple hundred miles of Oahu and launches his strike force. The Japanese pilots notice that the rising sun against a nearby cloud bank resembles their own battle flag -- a good omen. They are spotted on a newly-installed American RADAR, but the officer in charge ignores the sighting. A midget submarine is also attacked by an American destroyer as it attempts to infiltrate the harbor, but this too is dismissed as a false alarm. When the Japanese aviators arrive at Pearl Harbor, they find the sailors assembling for inspection on the Battleship decks and not a patrol plane in the sky.
Meanwhile the Japanese Ambassador (Shogo Shimada) is having problems decoding the final message (a declaration of war) from his government. Ironically, American Intelligence cracks the messages more quickly, but it's a Sunday morning, and none of the senior officers can be found to issue proper orders! As the attack begins at Pearl Harbor, the declaration of war still has not been delivered to the Secretary of State, thus leading to a "sneak" attack. The American brass in Washington eventually sent a message warning of impending attack, but it reaches Hawaii too late to be of use.
In one of the most skillfully-shot battle sequences (using replica planes and real explosions, not CGI) yet filmed, the American fleet is devastated. Most of the huge battleships are sunk or rendered useless, and most of the aircraft at the island's various airfields are quickly destroyed on the ground. A few Americans manage to shoot back, and a couple of pilots successfully get their fighters aloft, but to no avail. It is noted by the Japanese that the American aircraft carriers, a primary target, are not present at Pearl Harbor.
As word of the great victory is relayed to Yamamoto, he grimly says to a subordinate, "I fear all we have done is awaken a sleeping giant and fill him with a terrible resolve."
