I will give you two hints. It was not the army of Winston Churchill and it was not the army of Dwight D. Eisenhower. The Brits and the Yankees were Johnny Come Lately's to the struggle against Nazism in Europe.
“The lack of outside support may have left the Soviets weak, but they refused to collapse. Despite suffering catastrophic losses in the early months of the war, the Read Army defeated Germany in the Battle of Moscow in the fall and winter of 1941-1942. For the first time, the mighty German war machine had been stopped.”
And here is what F.D.R. told Churchill:
“... the Russians are killing more Germans and destroying more equipment that you and I put together.”
The Untold History of the United States
Oliver Stone and Peter Kuznick
Gallery Books, New York, 2012