Warfare in hunting and gathering or early agricultural society generally involves raiding rather than invading, and killing often -- but not always -- may be relatively infrequent or unnecessary. For example, counting coup among the Plains Indians, or the highly ritualized raiding in the New Guinea highlands.
The evolution of ritual warfare usually takes place in the context of a perceived stalemate in military advantages
, which has little to do with the primitive nature of the cultures
, and rules developed to manage a chronic sub-lethal (or at least in social terms, a sub-existential) or serial conflict. Even so, the rate of death in such "ritual" warfare is not inconsiderable from reports like those among the Yanomamo in the Amazon, for example.
But this situation changes historically when something tips the balance of advantage. A notable and relatively modern example of this transition is in the rise of the Zulu, under Shaka - who innovated tactics, weapons and regular drill to end the system of "ritual conflict" and ruthlessly consolidate his centralized kingdom by outright conquest or submission.
Apropos the topic, a significant traditional part of the Zulu's military equipment for the conduct of the semi-religious ritual warfare -- which Shaka adapted to more intensive and rationalized use -- was pharmacological. This has interesting parallels in their physiological effects to some of the issues discussed so far here.
Reputedly they used traditional plants including a potent non-sedating varietal of marijuana, a native amaryllis bulb preparation that contained buphanidrine
-- with hallucinogenic and pain killing properties similar to codeine and morphine -- but also is a serotonin transporter that has MAO properties like amphetamine and MDMA.
More interesting for my supposition on the combative role of oxytocin is a Zulu war mushroom containing muscimol, a GABA agonist -- and it is believed that the expression of oxytocin and vasopressiin is mediated by GABA binding sites in the posterior pituitary.
This has a subsidiary role, apparently, in post-conflict physiology, and which seems to support the old saw that "Without victory there can be no peace." It seems that social defeat stress stimulates oxytocin expression, by a GABA pathway,
(socio-biologically speaking -- allowing the defeated but surviving combatant to nevertheless bond psychologically and emotionally with the victor, increasing chances of ultimate survival.) This kind of substance would have been exceedingly helpful in integrating defeated but now allied warriors into the tightly disciplined Zulu impis.