On July 26, 1945, in the Cecilienhof Palace outside Berlin, the United States, the United Kingdom, and China issued a public proclamation that ran to a single page. The Potsdam Declaration — formally the “Proclamation Defining Terms for Japanese Surrender” — called on the Japanese government to “proclaim now the unconditional surrender of all Japanese armed forces” and warned that “the alternative for Japan is prompt and utter destruction.” Japan did not accept. On August 6, an American B-29 dropped an atomic bomb on Hiroshima; on August 9, a second bomb hit Nagasaki and the Soviet Union entered the war against Japan, and Japan announced its surrender on August 15.
The Setting
The declaration was issued at the end of the Potsdam Conference and was the public product of several weeks of negotiation among the United States, the United Kingdom, and the Republic of China. The Soviet Union was not a signatory, since it was still technically a neutral party in the Pacific war under the terms of the Soviet-Japanese Neutrality Pact of 1941, but it had agreed to enter the war within three months of Germany’s surrender under the February 1945 Yalta agreements.
The declaration was the third major Allied statement of the unconditional-surrender policy. Roosevelt and Churchill had first announced it at the Casablanca Conference in January 1943, and Truman had reaffirmed it in May 1945. By the summer of 1945, the policy had come under domestic and military pressure, with some officials arguing that the bomb made it unnecessary. The Potsdam Declaration was the public answer: the United States would negotiate the terms of the surrender with the existing Japanese government, but the surrender itself would be unconditional.
The Terms
The declaration was carefully drafted. It called on Japan to disarm completely and warned that the occupying Allied forces would be withdrawn “as soon as these objectives have been accomplished and there has been established in accordance with the freely expressed will of the Japanese people a peacefully inclined and responsible government.” The language was deliberate: the Allies would not themselves decide Japan’s government, but the existing military and ultra-nationalist structures would have to go.
On the specific question of the Japanese emperor, the declaration was deliberately ambiguous. The American position at the time of Potsdam was that the emperor’s status would be determined by the Allied occupying authorities, and that the institution could be abolished if necessary. Prime Minister Kantarō Suzuki and Foreign Minister Shigenori Tōgō were privately exploring ways to surrender that would preserve the imperial institution — the public ambiguity of the declaration was one reason they could not bring themselves to accept it.
The Japanese Response
The Japanese government issued a public response on July 28, 1945, the famous “mokusatsu” — variously translated as “we will ignore it,” “we will treat it with contempt,” or “we will reserve comment.” The exact meaning of the word is disputed among historians, Japanese government was internally divided. The Supreme War Council, the highest decision-making body, was split three to three, with the military hardliners opposing any concession and the civilian members (including the emperor himself) willing to accept a conditional surrender. The public “mokusatsu” was read in Washington as a flat rejection.
The Bombs and the End
The Trinity test in New Mexico on July 16, 1945, had been successful. The first operational use of the atomic bomb was at Hiroshima on August 6. The second was at Nagasaki on August 9, the same day that the Soviet Union declared war on Japan and invaded Manchuria. The combination of the two bombs, the Soviet declaration, and the cumulative pressure of conventional bombing and naval blockade finally broke the deadlock. Emperor Hirohito, who had remained silent in the public debates, intervened personally to break a tie vote in the Supreme War Council. The Japanese government announced its acceptance of the terms of the Potsdam Declaration on August 14, with the explicit understanding that the imperial institution would be preserved.
The formal surrender ceremony was held aboard the USS Missouri in Tokyo Bay on September 2, 1945. The Second World War was over. For the broader diplomatic and military context, see the Yalta and Potsdam conferences.