When the Congress of the US authorizes use of force OR when we are attacked. Get it? You are in way over your head.
So when Congress authorizes the use of force? Well at least you got that part right. But I gather that you mean that they authorize it carte blanche unless they grow a backbone (still waiting for that to happen) and say no?
No, the system was designed for the miltary to be called in to action by Declaration of War. We have to declare it whether or not an act of war was commited against us and that is precisely on of the rolls of Congress. No where in the Constitution does it say the president has the power to wield the miltary with the judgement and restraint of a two year old.
Way over my head to you? My, you are full of yourself aren't you?