We – The President of the United States, the President of the National Government of the Republic of China, and the Prime Minister of Great Britain, representing the hundreds of millions of our countrymen, have conferred and agree that Japan shall be given an opportunity to end this war. . . . 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 Potsdam Declaration, 1945

What is the purpose of this declaration?

to warn Japan that it must surrender, or face severe consequences
to persuade Japan to negotiate for a cease- fire
to encourage the Soviets to support a declaration of war against Japan
to convince the armed forces of Japan to support the Allied invasion