Complex sentence: The societies strenuously and effectively resisted all efforts to bring them under normal military discipline; as a result, the Germans were within the laws of war in executing captured francs-tireurs as irresponsible non-combatants found with arms in their hands.
Split into simpler sentences: The societies strenuously and effectively resisted all efforts to bring them under normal military discipline. Rhe Germans executed captured francs-tireurs as irresponsible non-combatants found with arms in their hands.