Churchill always knew who his enemy was. As a backbencher in the 30’s he not only warned Britain about Germany but Russia as well. However, as Churchill himself said once when asked about Stalin during WWII, if Hitler had invaded hell, I would make at least a favorable reference to the devil in the house of Commons. They were under an immediate existential threat from Germany, after Germany foolishly decided to invade Russia of course Churchill would allay with Stalin to save the British Empire.
As for the end of the war, I think you need to put that in context. No one at the time would realize the destruction that would rain on eastern Europe and the coming Soviet Empire. On top of that, we were war weary and had reached our objectives in Europe. The country who had attacked us was still to be defeated and no one knew how long that would take. There was a saying back then, ‘Win the war in 48 and a bread line in 49’. The common thought in April 1945 was that it would still take 3 more years to defeat Japan. All of the troops that did not have enough points to go home were preparing to go to the Pacific for the invasion of Japan. Because of these things, no one thought declaring a new war with Russia was even plausible.
All of the troops that did not have enough points to go home were preparing to go to the Pacific for the invasion of Japan.
Germans and Russians didn't use a point system. You served until you were either dead or the war was over.
Dictators can demand that.
Except Patton. And of course Roosevelt, Truman and certain general officers knew about the Manhattan project.