Walling Iraq

A couple of days ago, I was rereading Fred Kaplan's January piece "Mission Impossible: Bush's Smart New General Can't Save Iraq" and was struck by this passage:
In the one successful counterinsurgency campaign, in the northern town of Tal Afar, the 3rd Armored Cavalry Regiment surrounded the town with a 9-foot-high wall to isolate the city. This was in addition to other counterinsurgency techniques—maintaining a high troop-to-population ratio, dealing in a civilized manner with local authorities, and so forth. (Tal Afar slid back into chaos when the 3rd A.C.R. was redeployed to another hot spot—another indication that clear and hold, much less clear, hold, and build, requires a lot more troops than the United States has ever had in Iraq.)
Will Petraeus wall off neighborhoods in Baghdad? (The U.S. Army in Iraq does have a lot of concrete.) Is such a strategy feasible in a city of 6 million, as opposed to a town of 60,000 like Tal Afar? Moving in the bulldozers and the berms may be a dramatic first step. But then what?
This is about what I took from George Packer's article on the "Lesson of Tal Afar" as well -- you couldn't possibly scale-up what Colonel H.R. McMaster and the 3rd ACR did there. But according to one of Andrew's letter-writers that's exactly what they've done:
No one ever mentions the fact that we have literally built walls around each neighborhood and along every highway as the reason the violence is down here. The place looks like an Orwell novel gone wrong. The people cannot shoot each other through walls and the insurgents cannot move around to plant their bombs. A society cannot function walled off form each other.
I think one has to reply to this that while a society cannot function all walled off like this, it can't function in the midst of constant anarchy either. I believe this technique comes to the US Army's counterinsurgency theorists via Belfast, where I believe they have been effective in helping the British maintain a degree of order.
To some extent, this brings us back to the question of strategy. If tactics employed in Northern Ireland can be made to work in Iraq (and maybe they can) even though Iraq has ten times as many people as Northern Ireland does and even though Iraqis don't speak English and even though the sectarian violence in Iraq is undergirded by concrete fighting over valuable resources, then does this really seem like a wise strategic undertaking? It doesn't seem that way to me. It's been decades since "the Troubles," after all, and while Northern Ireland is now in a situation that there's reason to be optimistic about, you could imagine it all going to shit. All things considered, it seems like the British position there is one we ought to avoid getting ourselves stuck into. Emulating the UK's more successful tactics from that theater makes sense if we're going to adopt that kind of mission, but there mere fact that the tactics can maybe kinda sorta work if we give them a few dozen years is no reason to actually do it.
U.S. Army photo by Spc. Alan Moos