According to US intelligence the Afghan president Hamid Karzai controls only 30 percent of Afghanistan, with the Taleban holding 10 percent. Most of the country is under local tribal control. But building support among the tribes is now at the core of a new American counter-insurgency strategy. The Americans believe they've now got a blueprint for winning hearts and minds. The BBC's Alastair Leithead has been following US troops and their British allies to find out how the plan is working.