I think there’s an answer to Jonathan’s question below: what if Congress doesn’t appropriate the money to support more troops in Iraq but the President spends it anyway? The answer is in the Anti-Deficiency Act, which not only makes unappropriated spending a criminal offense, but assigns criminal liability not just to the person who orders the spending but to any official who “obligates” or “expends” the money. Is it unlikely that, under the circumstances, civil servants would go to jail, or lose their jobs? Sure. But “unlikely” may not be good enough to get literally tens of thousands of people to take the risk of paying the troops and paying for, or signing the contracts for, their supplies. So I doubt the President could get his orders obeyed.