In 1991, Iraq invaded Kuwait with the aim of appropriating and taking control of their oil resources. The United States, acting in Kuwait's behalf, repelled the Iraqi invader and drove them out and back into their own country. The United States "invaded" Iraq only in a very loose sense of the word "invade."

International Law recognizes "the Right of Hot Pursuit." This permits a nation or law enforcement agency to pursue wrong-doers, whether they are private criminals (such as, say, pirates) or the retreating armed forces of a hostile country across national borders without it being construed as an "invasion" as such.

Discovering the location of a wanted international criminal and entering another country to get him falls under the "hot pursuit" clause of International Law, and although the host country may bellow like a goosed moose, it does not constitute an "invasion," provided the pursuers withdraw once the criminal is dealt with. Especially if there is some suspicion that the country may actually be sheltering the criminal and denying it, while claiming to cooperate.

"It's in the book!"
             —Doodles Weaver

The actual invasion of Iraq, declared by the Bush Administration in response (according to Bush) to the 9/11 attack and Iraq's alleged stockpiling of weapons of mass destruction (which turned out not to exist), was an invasion. But obviously that did not occur until some time after September 11, 2001

Don Firth