We're already at war, brother. I know how this works firsthand.
Everybody thinks we "officially" went to war with Iraq in the spring/summer of 2003. But, when I was in the military, my executive officer basically told us in late 2002, "Boys, we're going to war with Iraq". Even though my ship was being decommissioned, our crew still participated in underway exercises to prepare for what would be Operation Iraqi/Enduring Freedom.
By the time the public-at-large hears about it, the folks in the military are already deployed or en route to being deployed to drop warheads on foreheads.