Question: when did the usa declare war on japan
Answer: December 8 , 1941

title: United States declaration of war on Japan
text: United States declaration of war on Japan On December 8, 1941, the United States Congress declared war () on the Empire of Japan in response to that country's surprise attack on Pearl Harbor the prior day. It was formulated an hour after the "Infamy Speech" of US President Franklin D. Roosevelt. Japan had sent a message to the United States to its embassy in Washington earlier, but because of problems at the embassy in decoding the very long message – the high-security level assigned to the declaration meant that only personnel with very high clearances could decode it, which slowed