Answer:
Later that day (December 8 in Tokyo), Japan declared war on the United States and the British Empire, but the declarations were not delivered until the next day. After realizing that their territory had also been attacked, the British government declared war on Japan, and the United States Congress declared war on Japan the next day (December 8). Despite the fact that they had no formal responsibility to do so under the Tripartite Pact with Japan, Germany and Italy declared war on the United States on December 11, and the United States replied by declaring war on Germany and Italy.
Despite the fact that they had no formal responsibility to do so under the Tripartite Pact with Japan, Germany and Italy declared war on the United States on December 11, and the United States replied by declaring war on Germany and Italy. The attack on Pearl Harbor was eventually declared a war crime in the Tokyo Trials because it occurred without a declaration of war or express warning.
