Why the Allies demanded unconditional surrender

Did the Allied demand for unconditional surrender unnecessarily prolong the war?

It may have affected the war's duration, but the major Allies were not prepared to accept peace terms that left Germany or Japan holding the gains their wars had created.

The answer to the claim that unconditional surrender prolonged the war is qualified. Whatever its effect on duration, the Soviet Union would not accept a negotiated German survival, while Britain and the United States would not allow Japan to retain its conquered territories. The demand reflected the minimum political outcomes the principal Allies believed victory had to secure. The exchange connects battlefield strategy to the peace terms for which the coalition was fighting.