Some Mediterranean tribe of sentients couple of hundred thousand years - I doubt author meant humans since they were not around then - has two "civilized" warring kingdoms.
One of them receives a "barbarian" from the North - with a different way of looking at the war. He has local queen's support, though military doesn't like him. He will treat a battle as a raid - utterly destroying the victim city & ruthlessly looting it. Making his employing kingdom very unhappy - they only wanted to dictate trading terms, now there is no one left to trade.
- Anthony Boucher (Ed)'s "The Best From Fantasy & Science Fiction, Sixth Series". An online copy is linked by Free SF Reader (with at least one incomplete story - Theodore Sturgeon's).
Fact sheet.First published: ...
Note: Why is this post so short?