Why Marja?

Or even better, why Helmand? That's what Steve Coll was trying to figure out yesterday on his New Yorker blog.

It is true, of course, that U.S. forces cannot operate in large numbers in Pakistan, and are dependent on Pakistan’s fitful, ambivalent cooperation against the Taliban. Yet that still raises the question of why the thousands of U.S. Marines available in southern Afghanistan are concentrated largely to the west of Kandahar, rather than reinforcing struggling Canadian troops in the province itself.

In my Washington rounds, I’ve heard several overlapping explanations. Some argue that the U.S. cannot afford to yield ground in Helmand taken by the Marines last year, before the current counterinsurgency approach was fully cooked. U.S. commanders have also said that Helmand must be cleared and held in order to open transport routes to the West, toward Herat. (That makes sense.) Perhaps control of Marja will eventually become a staging area for a gradual push east into Kandahar, to take back those parts of the city and its surroundings where the Taliban now exercise disturbing degrees of influence.

I have also heard it suggested, however, that the big and visible Helmand operation is being conceived as a sort of “demonstration project” of joint U.S. and Afghan security and governance capabilities - that “clear, hold, and build” there will be constructed as a sort of theme park of revived counterinsurgency practice. In this explanation, it is hoped that the operation and its aftermath will so dazzle fence-sitting Afghans and the Taliban alike that it will contribute to a shift of perceptions about which side in the war is gaining momentum. If this is part of the command’s thinking, it seems a potential prescription for Potemkin architecture.

I've seen it said that Marja is the enemy salient in an otherwise solid belt of government-controlled areas crossing the southern provinces, and that this explains the focus there. So what's the story?