Berserker — Fred Saberhagen

THE DEATH MACHINES
Long ago, in a distant part of the galaxy, two alien races met -- and fought a war of mutual extinction. The sole legacy of that war was the weapon that ended it: the death machines, the BERSERKERS. Guided by self-aware computers more intelligent than any human, these world-sized battlecraft carved a swath of death through the galaxy--until they arrived at the outskirts of the fledgling Empire of Man.

These are the stories of the frail creatures who must meet this monstrous and implacable enemy --and who, by fighting it to a standstill, become the saviors of all living things.