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It was not the norm, but rather a failure mode. This isn't to say it wasn't common, but not the norm.

A History of Warfare by John Keegan is a good introduction to military anthrolopogy, with an extensive bibliography.

It is the norm for pre-industrial societies.

No it isn't, and I invite you to read the book to find out why. Murderous raids are the exception when the more widespread norm of ritual combat or tit-for-tat kidnappings with limited casualties had broken down.

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