The book Bloodlands describes some of it. A book I cannot face reading for a second time.
One of the greatest crimes of the war was FDR's abandonment of Poland to Russian hegemony at Tehran. Churchill knew, but at that point was leading a nation made bankrupt by America's prewar isolationism, and could do nothing.
Britain was bankrupt by their Empire that they couldn’t hold onto. The same way the US is bankrupt, except we lost every war since 2.