It was deeply ingrained by their internecine conflicts. When factions would fight in their internal wars, they would expect the losing side to commit suicide if

It was deeply ingrained by their internecine conflicts. When factions would fight in their internal wars, they would expect the losing side to commit suicide if they happened to be defeated and not dead by enemy hands. Their military class was not introspective enough to consider that implication of this, if applied to its logical end in a conflict with an out-group, would be the total extinction of their ethnic group.