> Why? Because territories in WW2 were split up in significant part based on who conquered which part. Hence East Germany going to the USSR and West Germany going the the West.

That was particularly painful for Churchill to accept at the end when he had to hand over Poland to Stalin. Poland was the reason Britain officially entered WW2 in 1939

https://en.wikipedia.org/wiki/Western_betrayal

> We and France are to-day, in fulfillment of our obligations, going to the aid of Poland, who is so bravely resisting this wicked and unprovoked attack upon her people. We have a clear conscience. We have done all that any country could do to establish peace, but a situation in which no word given by Germany's ruler could be trusted and no people or country could feel themselves safe had become intolerable. And now that we have resolved to finish it, I know that you will all play your part with calmness and courage

(Chamberlain, Sep 3, 1939)