What was the 1945 Allied ultimatum that Japan accepted called?

The 1945 Allied ultimatum that Japan accepted was called the Potsdam Declaration.

Issued on July 26, 1945, the declaration set out the Allies’ terms for ending the war with Japan. It called for the unconditional surrender of Japan’s armed forces and warned that refusal would bring “prompt and utter destruction.” The text also described disarmament, occupation, war-crimes prosecution, and limits on Japanese sovereignty.

The United States, the United Kingdom, and China issued the declaration. The Soviet Union was not yet at war with Japan when it was released, so Soviet leader Joseph Stalin did not initially sign it. The Soviet Union later declared war on Japan on August 8.

Japan’s government did not immediately accept the ultimatum. After the atomic bombings, the Soviet declaration of war, and internal political debate, Emperor Hirohito instructed the government to accept it. That decision was announced by radio on August 15 and formalized by signature on September 2.