The last time Congress formally declared war was in December 1941, following the attack on Pearl Harbor more than a half-century ago.
How, then, did Congress avoid its constitutional power - or duty - to declare war over Korea, Vietnam, and the Persian Gulf?
The answer is that Congress played it safe. It gave the three presidents - Truman, Johnson, Bush I - something, without having to go on record as formally declaring war.
Reason why Presidents no longer need Congressional Declarations of War - Legal Precedence-Youngstown Sheet and Tube Co. v. Sawyer.
In short, part of that decision states that if Congress sees a President preparing for war and does nothing to stop him that they(Congress) are actively agreeing to it.
If the president starts a war, he’ll be in violation of his oath of office and should be impeached. It’s the duty of all citizens to demand that our Constitution be followed.
Highly unlikely, should it ever get to the USSC Article II would trump Article I and Congress would be unwilling to answer why they didn't stop the buildup of force.
The above referenced link lays it all out in great detail.
Someone should also clue Saddam in on the fact that, the bombs will be real this time, not filled with cement like the ones his Marxist buddy bill clinton dropped on him in 1998.