The correct answer here is to establish Germany's war guilt.
With this article, it is established clearly that the war was Germany's fault, and of her allies. Germany accepted this. What all of this means is that now as the both guilty and losing party Germany had to accept things the Allies demanded of her. The Allies had all the power in this negotiations.
If one country became Communist, others would follow.
<span>Answer is - To declare war</span>
Walls Had Protection From Armies
