Well, up to a point, Lord Copper. First, the communists and the west (meaning the British Empire, the US and their allies) were on the same side for most of the war, so in a narrow sense they both won. Yes, eastern Europe was controlled by the Soviet Union after the war, so in that sense the communists had a partial victory and various countries, notably Poland, were saved from Nazism only to be subjected to a comparable tyranny. But the communist sphere of influence was limited, any expansion in Europe was prevented, essentially by the American nuclear deterrent, and communism was eventually defeated, or it imploded, in the 1980s.