UNCONDITIONAL SURRENDER came into the American political lexicon during the Civil War, when the Union General Ulysses Simpson Grant rejected a request for negotiations and demanded the "unconditional surrender" of the Confederate-held Fort Donelson, Tennessee, in 1862. U. S. Grant's strict terms became his nickname.
Since then, every major international war to which the United States was a party was ended by a negotiated settlement, except for World War II. In that conflict, the Allies' demand that the Axis powers surrender unconditionally, first announced by President Franklin D. Roosevelt at a Casablanca summit meeting with British Prime Minister Winston Churchill on 24 January 1943, has been praised for holding together the alliance and criticized for prolonging the war.
Legend holds that Roosevelt surprised Churchill by the sudden announcement, but an agreement to demand unconditional surrender had actually been reached after discussions within the State Department, the Joint Chiefs of Staff, and the British Cabinet. With their statement, the Anglo-Americans hoped to reassure Soviet Premier Joseph Stalin that the Western Allies would not seek a separate peace with Germany. The Allies also hoped to prevent any public debate over appropriate surrender terms and, above all, wished to prevent Germans from later claiming that they had not been militarily defeated, as Adolf Hitler did after the 1919 Versailles settlement of World War I.
Critics have claimed that the demand for unconditional surrender bolstered the Axis nations' will to fight and eliminated the possibility of an earlier, negotiated end to the war. In the case of Germany, this argument is largely speculative. Evidence suggests that a faction in the Japanese government sought peace even before the atomic bombs were used, provided that Japan be permitted to retain its emperor—a condition rejected by the Allies before the atomic bombings, but ultimately accepted in the peace settlement of 2 September 1945. Whether an earlier concession on the emperor's status could have ended the war without the use of the atomic bomb is intensely debated among historians.
Hikins, James W. "The Rhetoric of 'Unconditional Surrender' and the Decision to Drop the Atomic Bomb." Quarterly Journal of Speech 69, no. 4 (1983): 379–400.
O'Connor, Raymond G. Diplomacy for Victory: FDR and Unconditional Surrender. New York: Norton, 1971.