One of the better short stories I recall was a society so paranoid that they attacked in every direction, and were quite successful at it. They didn't have many friends, but then they didn't have many neighbors, either.

Julius Caesar, in his account of the Gallic Wars, describes one of the many different tribes in Greater Gaul (France, Germany, Belgium, parts of Spain and Switzerland) as believing that it was a sign of strength to have no neighbors, to have wide areas of relative emptiness all around them -- it meant they had driven all their neighbors away. If I remember right (which I often don't--but I have taught this material), this tribe looked down on any kind of farming, and also on private property, and they moved around constantly. They thought that it would make them weak and effeminate if they became attached to land or to houses, or if they got too used to being warm in the winter, too comfortable.