To learn why a resurgent Taliban is fighting American and NATO troops to a military draw in Afghanistan, you have to go to the frontier region on both sides of the Pakistan-Afghanistan border.

Our colleague, Carlotta Gall, did just that last month and what she learned led to a physical assault on her by Pakistani intelligence officials and five hours in custody for her photographer, Akhtar Soomro. We now know why.

Gall’s reporting has determined that Quetta is an important rear base for the Taliban, and that Pakistani authorities are encouraging and perhaps sponsoring the cross-border insurgency. Many problems need to be addressed. But positive results in Afghanistan will be limited as long as Afghanistan’s much more populous and powerful neighbour, Pakistan, provides rear support and sanctuary for the Taliban insurgency.

Pakistan is now the third-largest recipient of American foreign aid. Yet more than five years after 9/11, the Bush administration has still not been able to secure Pakistan’s active and consistent support against the Taliban. The very least Washington should be demanding of President Musharraf is that he enforce an immediate halt on Pakistani military support for the Taliban insurgents who are crossing the border and killing American troops.