This is the way it works. Plans will have been made. They are constantly being updated and massaged. At some point a go date and hour will be decided. The rubberband will start to wind up so as to be snapped at the go hour. Any time up to that the operation can be halted, and in fact wont proceed unless the final approval is given. Given approval, the operation begins a short phase where it will proceed unless a late decision is made to halt it. This phase usually lasts from time of first launch of combat aircraft to first bombs away ( a few hours ). Lacking a last minute change of mind, the war will begin.
Doesn't approval from Congress fit in here somewhere?