Philip K. Dick 
Second Variety [EPUB ebook] 

A nuclear war between the Soviet Union and the West has reduced much of the world to a barren wasteland. The war continues, however, among the scattered remains of humanity. The Western forces have developed ‘claws’, which are autonomous self-replicating robots to fight on their side. It is one of Dick’s many stories in which nuclear war has rendered the Earth’s surface uninhabitable. The story was adapted into the movie Screamers in 1995.