tonight marks the very first time I have heard an officer of the Border Patrol use the magic words to describe current (and projected future) security measures: "defense in depth"
the last time I heard those magic words in the same context, they were used to describe the LOSING strategy the post-succession (Later(Western)) Roman Empire used to "deal with" the invading barbarian tribes - which eventually deromanized their provinces and at length erased the western empire from the map.
If I were a *suspicious* man, I'd be likely to suppose that whoever is setting these policies is actively TRYING to cause the de-Americanization of the American Southwest...