Thank you! Apologies for any mistakes, I was only half remembering and wasn't sure if I'd dreamt it up.You are referring to Operation Unthinkable in which Winston Churchill had a crazy plan for the Western Allies to attack the Red Army with 100,000 rearmed Germans POWs to "bring the will of the United States and Great Britain upon the Soviet Union." In 1945, the third bomb wasn't read until November.
There's also the issue of the Berlin Blockade in 1948 going hot.
Both of these scenarios would feature a limited one-sided nuclear conflict.