In one of the books I read about Helmand, I think "Little America", it said the reason the Marines went into Helmand was because their leadership wanted place where the large number of Marines going would all be under Marine control. Helmand was the the only place available that was empty enough of other US forces whereby they could do that. Which is what former_0302 said.

And it further illustrates Bill's point that unified command is something we can't do at all. I thought unified command was the bedrock of small war fighting and if you didn't have unified command you were wasting your time? That is one thing all those much maligned small wars theorists said. But we never did it. For that matter unified command is vital in big war fighting too. I hope we remember how to do it before we get beat in the next big war.