Once one goes thru the congressional process which could take months; the element of surprise and opportunity is long gone.
If congress gets involved are they going to insist on determining how many and which units are to be used.
Will they insist on approving any reinforcements?
In the case of the Iran attack Iran could have developed their bombs and mussiles
This is not the 18th century when communication between parties could take months.
Fir example, the Battle of New Orleans was fought after the treaty was signed
The world and decisions moves in seconds now, not months.
