I have seen a lot of threads with talk about insurgencies in this forum and I am wondering whether or not they would actually happen or if they did if they would be effective. Part of the reason why they are effective today is that combatants more or less follow certain rules of engagement which make targeting of noncombatants unfeasible for many reasons, thus the insurgents have a means to hide in local populations. However, since the rules of engagement as we know them are a rather modern invention, I fear that the combatants of previous eras would have less scruples about weeding out and destroying such insurgencies.
It seems that the use of effective insurgencies is a rather popular notion in common topics, such as a scenario where Canada is conquered by the Americans, despite the latter having a history of effectively countering such tactics via the various wars with the tribal nations. To me, this insurgency argument has always seemed more of the nationalistic vein of "My country would never be part of (Insert Nation Here)!" So, is there any credibility to such insurgencies and resistances, or is it all just blatant wish fulfillment?