Just like Truman who was there when WWII ended, although it was mostly the work of FDR. And say what you will about FDR's domestic policies, IMHO he was a hell of a wartime President.
"I just have a hunch that Stalin is not that kind of a man. ... I think that if I give him everything I possibly can and ask for nothing from him in return, noblesse oblige, he won't try to annex anything and will work with me for a world of democracy and peace."
Helluva wartime leader.