The only way to do is to run away of Germany and throwing nuke and anthrax combo on Russia as well as Russian troops in Germany, such as bombing and nuking W and Baku.
Communists in Western Europe would rebel.
However, the nukes were not available yet at this time. Conventional war would be a nightmare for Allies. Well, at least the British army would be steamrolled. Soviet land forces by this time were superior in basicallu every aspect, and unlike Wallies, their aircrafts were designed for greater focus on battlefield destruction.