I think it helped that things were more tribal back then. Enemies could sack and pillage if opportunity presented itself. That presented peasants/commoners/et

I think it helped that things were more tribal back then. Enemies could sack and pillage if opportunity presented itself. That presented peasants/commoners/etc. a disincentive to defect. It's not like an outsider would be friendly to a defector in most cases. This provided a bond to the local warlord/chieftain/etc. Essentially it was a fear-factor to not defect because things would be worse. Plus, these people had few possessions. They basically only had their labor and the clothes on their backs. They had very little power. A population that had tenuous leadership would soon be easy pickings for a neighboring rival to swoop in and potentially make things worse.