Japanese attack on pearl harbor, is the right answer.
On 8th December 1941, the Congress of the United States announced war on Japan in acknowledgement to that nation's astonishment attack on Pearl Harbor the previous day. It was expressed an hour following the Infamy Address of Franklin D. Roosevelt, the then President of the United States. Japan had sent information to the embassy of the United States in Washington preceding, but due to the dilemmas at the consulate in decoding the extremely lengthy note – the high-security level allocated to the announcement meant that only employees with very high allowances could decode it, which reduced the manner – it was not abandoned to the Secretary of State of the United States until subsequent the attack on Pearl Harbor. Following the declaration of the United States Germany and Italy the allies of Japan declared war on the U.S. which brought the United States in the World War.
