Even though Japan planed to warn U.S. 30 minutes before attack, decryption and English typing was delayed because Japanese embassy staff was out of the office when it receieved telegram from Tokyo. Therefore, surprise attack was carried out before warning. Combined Fleet Commander Admiral Yamamoto's anxiety about this kind of trouble turned into reality.
This incident eliminated U.S. citizens' war weariness and united them under the slogan "Remember Pearl Harbor".
This is because of not in time at the schedule when the one that the notice 30 minutes ago of the attack beginning was scheduled sent the cable to a Japanese embassy from Tokyo to the United States at first the attache was not in the embassy, trying to strike it to decipher and English was late.
When the notice was passed, the surprise attack had already been done.
Though Yamamoto, the union fleet secretary of the command worried about such a trouble, his presentiment had been hit.
In United States, atmosphere that dislikes war by that that drifted till then changes completely, and the public sentiment has united in 'Remember pearl harbor' password.