Of course interesting things happen when the alliance has outlived its usefulness (I think only A-bombs curbed that in the case of Stalin and Churchill).
I've read Churchill's book on the endgame of World War II. Even before the fall of Berlin, Stalin was positioning forces for immediate follow-up. Churchill's attempts to persuade FDR that "Uncle Joe" might act in bad faith, were as unsuccessful as Churchill's attempts, from 1932 to 1938, to persuade his nation that dialogue and compromise with Hitler were futile. Churchill noted with deep regret that Britain declared war in 1939, to defend Poland... and that Britain did not, in the 1945 outcome, secure Poland's autonomy and freedom.
Churchill's treatment of India as a conquered territory had unpleasant parallels with Hitler's attitude towards the Slavic "untermenschen". In 1931, he said "“It is alarming and also nauseating to see Mr. Gandhi, a seditious Middle [Inner] Temple lawyer, now posing as a fakir of a type well known in the East, striding half-naked up the steps of the Viceregal palace, while he is still organizing and conducting a defiant campaign of civil disobedience, to parley on equal terms with the representative of the King-Emperor.” And then some years later, very different things, such as “Mr. Gandhi has gone up very high in my esteem since he stood up for the untouchables”. He had a noble character in some ways, and a savage character in other ways, and he changed over time.
There are people who see the real world in black and white, eternally, and who bring that perspective to their D&D campaigns. They baffle me. *shrug* To each their own.