When you cannot walk the streets without armour in daylight for fear of being shot at,
When you are attacked, sniped at, booby-trapped, bombed,
When you cannot enter the area where your adversary hides,
When you can't dislodge your adversary
When you lose lives in your efforts towards the above
When you cannot pull your troops out of a country for fear of the mess you'll leave behind

Then it's not an "insurgency", a "peacekeeping", a difference of agreement or a spat.

"It's the war, stupid"