Question

Which Ally bore the brunt of Germany’s assault during the first years of the war?

Answer 1

If, the war described in the question is referred to second war then:

This war was considered as the greatest war configuration in the history in the humanity unleashed by nazi Germany, fascist  Italy and militaristic japan.

At the early years of the war the ally countries were France, england and soviet Union.

The largest losses corresponded to the Soviet Union  wich lost 27 million people.

Answer 2

The United States bore the brunt of Germany's assault during the war.