Then again, the OP says nothing about nazis and WWII. So, a surviving Weimar Republic which peacefully integrates Austria and employs the best minds in Central Europe watches as France goes communist. Surrounded by communist countries by both west and east, and confident in the lack of readiness of the Soviet Union, it launches a preemptive strike against the Comitern, with the tacit support of the USA and a reluctant UK, which rather see a capitalist power dominating Europe rather than a communist alliance doing so. Germany is not subject to a blockade, the RN even escorting British flagged merchants to neutral Holland.
By 1944, a peace treaty has been brokered with the USSR and D-Day is the German invasion of Algeria, where staunch French forces remain after being expelled from, let's call it, European France in 1941. The bombs are used to clear the beaches. However, due the limited knowledge of radiation, the troops are sent right after the bombs are launched and die shortly after of radiation poisoning.