For several thousand years, the three indispensable "hardware" elements of any war have been soldiers, weapons and a battlefield. Running through them all has been the "software" element of warfare: its purposefulness.
Moreover, when a nation state or national armed force, (which adheres to certain rules and will only use limited force to obtain a limited goal), faces off with one of these types of organizations, (which never observe any rules and which are not afraid to fight an unlimited war using unlimited means), it will often prove very difficult for the nation state or national armed force to gain the upper hand.