As the National Guard deployment on the border comes to an end, an article in Military Review (a journal published by the Army) looks at what the Army's experience along the Mexican border in 1915-1917 (Pancho Villa and all that) might teach us about today. (The pdf is here.) The author, a professor at the Army staff college at Ft. Leavenworth, concludes sensibly that:
Either the military must be empowered to enforce border security by all means available, which will in effect militarize the border, or the military must be withdrawn to allow the undermanned Border Patrol and local authorities to handle the job. The toothless military presence on the border cannot last forever. The U.S. military has enough on its plate fighting the nation's conventional and unconventional wars; it cannot and must not become a permanent southern border neighborhood watch association.
We seem to have chosen the second option — withdrawal — for now, but if the Mexican state continues to disintegrate, we'll be revisiting this issue.