Philip K. Dick 
Second Variety (With a Biographical Introduction) 

A nuclear war has reduced planet Earth to a pile of ashes. The American government has fled to the Moon, leaving behind soldiers to fight a wearisome war against Russia. The Russians seem to be winning, but at some point, from the depths of the factories underground, the claws emerge, monstrous robots that turn the tide of the conflict. Everything seems to be going in their favour, until one day a Russian courier arrives in the camp, bringing with him a request for peace. Is it really the end of the conflict or is it a trap?