already deciphered A declaration of war declared war United States
The attack took place before any formal declaration of war was made by Japan, but this was not Admiral Yamamoto's intention. He originally stipulated that the attack should not commence until thirty minutes after Japan had informed the United States that peace negotiations were at an end. However, the attack began before the notice could be delivered. Tokyo transmitted the 5000-word notification (commonly called the "14-Part Message") in two blocks to the Japanese Embassy in Washington. Transcribing the message took too long for the Japanese ambassador to deliver it at 1:00 p.m. Washington time, as ordered, and as such, the message was not presented until more than one hour after the attack had begun — but in fact, US code breakers had already deciphered and translated most of the message hours before it was scheduled to be delivered. The final part of the message is sometimes described as a declaration of war. While it was viewed by a number of senior U.S government and military officials as a very strong indicator negotiations were likely to be terminated and that war might break out at any moment, it neither declared war nor severed diplomatic relations. A declaration of war was printed on the front page of Japan's newspapers in the evening edition of December 8 (late December 7 in the US), but not delivered to the US government until the day after the attack.
