Several years ago, I watched the film "The Battle of Algiers", about the Algerian War of Independence 1954-1962. It depicted the rise of the Algerian National Liberation Front. The first step of any insurrection is to establish your own government infrastructure, and destroy the other guy's infrastructure. In the case of the FLN, this entailed bushwhacking uniformed French police officers in the Casbah. Very soon,things got entirely too dangerous for the police- so the French government sent in the paratroopers- and things got *really* unpleasant in the Casbah.
Down Mexico way, the violence in border cities (especially Ciudad Juarez) has gotten so bad that the local police simply can't deal with it- they are either out-gunned, corrupt, or both. So the Mexican Government has now sent in the Mexican Army. What happens if *they* can't handle the situation- and as long as American demand for illegal drugs stays strong (it will) what happens?
Pat Buchanan recently predicted that in 5 years, we won't have 50,000 troops in Iraq- we'll be MUCH too busy on the Mexican border. I'm afraid he's right.