They didn't, although the bad guys did declare war on us, the same way Osama did, verbally, and also symbolically by cutting down the flagpole in front our legation. That was the First Barbary War, during Jefferson's administrations. During Monroe's administration, Congress was again asked for permission, but not to declare war, it being understood that a state of war already existed, courtesy of the Musslemen.
In that way, it's very analogous to both the first and second Persian Gulf Wars, and the war in the Afghan theater. The War existed. the President asked permission to fight it, at a time and place of his choosing.
Thanks for the update!
Against whom? The Northern Alliance was the legitimate Govt of Afganistan. Cannot declare war either on Al Qeda or the Taliban? Had no need to against Saddam. He was in violation of the 1991 cease fire. The Senate was being run by the Democrats at the time remember? THEY demanding the Authorization of Force resolution so they could show "we are fighting the war too".