At the January 1943 Casablanca Conference, President Franklin D. Roosevelt unilaterally declared the Allied policy of unconditional surrender, against the Axis Alliance. Though Churchill was officially on board with this policy after the conference, he had serious reservations.
Churchill’s next biggest worry after Hitler, was Stalin. There were still considerations in London of Germany as the anti-Soviet bulwark in Europe, absent of course Hitler and the Nazis.
Such considerations were not arrived at lightly, and were likely based on guarded knowledge which may never be revealed unless the fog enshrouding Deputy Führer Rudolf Hess’s flight to Britain, and/or that around German Intelligence Chief, Admiral Wilhelm Canaris are lifted.
If the possibility of early peace ever really existed, it evaporated with Roosevelt’s proclamation. It communicated to every citizen of Axis nations that no quarter would be granted them.
The one unexpected effect the policy, was Italy’s surrender after the fall of Sicily. Undertaken by anti-Mussolini factions within the Fascist Council, who sought to spare Italy becoming a ‘second front’ battle ground from end, to end.
They failed in that respect; the Allies were not prepared to land far enough north to stop the Germans flooding troops down the Italian boot. But, Italy was taken out as an Axis power.
Roosevelt’s motivations have been subject to speculation, and conspiracy theories since VJ Day. Especially after it emerged Churchill was not even advised before the proclamation. There was however, something afoot not publicly known at the time.
Soviet dictator Joe Stalin had been quietly seeking a separate peace with Hitler, and continued to do so into 1944. Peace feelers were extended through neutral back channels. But, they only coming to naught due to Hitler scoffing them off.
Catastrophic losses of Soviet troops was bleeding the USSR more than is generally known even today. Soviet victories while sweeping, incurred horrendous losses which were straining Stalin’s hold on power. That he never suffered a coup, is actually quite remarkable.
Had a Nazi-Soviet peace occurred prior to D-Day, millions of German combat troops would have been shifted against the Allies. Normandy, and any other potential landing zone in occupied Europe, could have been heavily reinforced.
With the Soviets put away, Turkey might well have been emboldened to join in the war to reclaim it’s lost Ottoman Empire, sweeping into the Middles East, with German forces freed up from the Russian Front riding point.
Fascist Spain, if reinforced sufficiently with some of those freed up Russian Front forces, would gladly have joined the Axis to take long coveted Gibraltar from Britain. With Gibraltar and the Suez Canal in Axis hands, the Mediterranean would have sealed off at both ends.
Roosevelt’s unconditional surrender policy was very likely a play to avert a Nazi-Soviet peace, by communicating the Allies were waging a fight to the finish, even it meant advancing across all of Europe, right up to the Soviet border.
Stalin no doubt, was aware of Roosevelt’s plans. The Roosevelt White House was saturated with Soviet spies. Stalin declined to attend the Casablanca Conference, obviously so as not to have himself bound by Roosevelt’s policy, in the event Hitler warmed up to a separate peace.
Upon the Normandy landings, a race for Berlin was on. Stalin made no further attempts at a separate peace.
Had Roosevelt lived to see VE Day, it’s an open question as to whether he would have relaxed terms for Imperial Japan. One could ponder that he might have. Since the Soviets were not a factor in defeating Japan.