The Potsdam Declaration outlined the terms for Japan’s surrender in WWII commencing with the warning: “We will not deviate from them. There are no alternatives. We shall brook no delay.”

The mention of “unconditional surrender” and a warning came at the end of the declaration:
“We call upon the government of Japan to proclaim now the unconditional surrender of all Japanese armed forces, and to provide proper and adequate assurances of their good faith in such action. The alternative for Japan is prompt and utter destruction”

The reference to “prompt and utter destruction” is generally taken as a veiled warning that the United States had the atomic bomb, which it had successfully tested on July 16, 1945.

The United States, Britain and China released the Potsdam Declaration on July 26, 1945.

The position of the Japanese Government was summed up in a statement to the Japanese press by Prime Minister Suzuki (Suzuki Kantarō):
“…… The Government does not find any important value in it, and there is no other recourse but to ignore it entirely and resolutely fight for the successful conclusion of this war.”

Japan’s spurning of the ultimatum led to President Truman’s decision to drop atomic bombs on Hiroshima and Nagasaki on August 6 and August 9.