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Lets assume for a minute that Germany had prepared somewhat better for the attack on the Soviet Union and it came say 2-3 weeks earlier so Leningrad falls freeing up troops, the transportation logistics around Moscow are screwed up, the attack to the south is more successful etc all of which sets back the Soviet war effort so that come the spring of 1945 the Red Army is still fighting to reach Poland. The WAllied attempts to gain a military foothold in France and Italy in 1944 fail.

Lets also assume because of the greater military success Germany has that the Allied atomic program is given more resources and spead up somewhat so that the first atomic test happens at the start of 1945 and two nukes are ready to be delivered by May. The exact dates don't matter exactly. The July 1944 plot occurs at a later date then OTL and is even less successful so only the direct plotters and a few dozen other officers are shot so no deep purge of the Heer.

May 1945 the nukes start dropping on German cities in an attempt to force the government in Berlin to accept unconditional surrender. First Dresden, then Nuremberg, with plans for the third bomb in the piple line to be dropped on Munich.

Hitler promises that Germany will fight to the death rather then surrender.

How does the leadership of the Heer and the SS react?
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