Which ally bore the brunt of germany's assault during the first years of the war?

The worst part of Germans assault during the first years of WWII was taken by the Soviet Union, fighting by itself against the Axis powers, and waiting for the cooperation from the other allies who were overdue and belated to join the combat, even though they'd  promised it previously, which might be one of the reason for future stressful relations between them after the war was over.

answer; /// i do believe that the correct answer is (d) cooperative play; /// good luck

answer; speaker;