> They maintained unit cohesion through social pressure rather than training and drills.
Historical times were brutal. If they were defending their home, losing the battle would result in their home being pillaged and their family enslaved or raped. That would be a great motivator to not run
> losing the battle would result in their home being pillaged and their family enslaved or raped.
Only true in certain times and places, mostly sacking besieged towns cities where it was done in order to pressure the defenders of the next siege to surrender with terms rather than fight to the end.
Not all historical societies had slavery. It declined hugely in medieval Europe - the Normans abolished it in England, for example (people forget this because of the revival of slavery in early modern times, and of course its continuation in other cultures) not long after they conquered the country.
Historical times were brutal. If they were defending their home, losing the battle would result in their home being pillaged and their family enslaved or raped. That would be a great motivator to not run