The Vikings knew, for instance, that prolonged exposure to combat can goad some men into a state of uncontrolled psychic fury. They might be the most placid men in the world in peacetime, but on the battlefield they begin to act with the most inexplicable and gratuitous cruelty. They become convinced that they’re invincible, above all rules and restraints, literally transformed into supermen or werewolves. The Vikings called such men “berserkers.”
LOSING THE WAR by Lee Sandlin
(The New Kings Of Nonfiction, edited by Ira Glass)
Bewildered Creatures 