Pakistani officials say Mahsud, who is accused of masterminding a campaign of suicide bombings in Pakistan and the assassination of onetime Prime Minister Benazir Bhutto, narrowly escaped a missile attack last week believed to have been carried out by drones, the main U.S. weapon for reaching across the border from Afghanistan. Dozens of other militants were killed in the strike.
U.S. military officials last week said they were seeing signs that stepped-up Pakistani operations were reducing the overall flow of weapons and militants into Afghanistan. But that has yet to translate into a significant overall drop-off in casualties among Western and Afghan troops, together with Afghan civilians, as a result of insurgent attacks.
The Pakistani military offensive so far has skirted North Waziristan, home ground of one of the most notorious insurgent groups, the Haqqani network. It is believed responsible for most major attacks in a wide arc of eastern Afghanistan, including Khowst province.
Despite pressure on the Pakistani side of the border -- including not only the Pakistani military offensive, but U.S. drone attacks and intertribal rivalries -- insurgents continue to make their way back and forth across the thinly guarded frontier. But their comings and goings do not go unobserved.
"We know who they are, and we know where they come from," said a U.S. military official familiar with intelligence on cross-border movement of Taliban commanders, foot soldiers and armaments. The official requested anonymity, citing the sensitivity of the intelligence involved.
Afghanistan's border police force, which is being trained by U.S. mentors, has had some recent successes in tracking and interdicting fighters and weapons. Still, the frontier has dozens of mountain passes and goat-track pathways, all well known to the Pashtun tribes from which the ranks of the Taliban are mainly drawn.
"You can't make some kind of human chain-link fence," said U.S. Army Capt. Philip Poag, who has been helping train the Afghan border police.
American forces in Camp Salerno's command area have been pushing into remote districts long used by insurgents as infiltration routes, uncovering encampments and weapons caches as they go.
Several weeks ago, American and Afghan troops made a rare find: a Taliban rest-and-resupply stop in a remote part of Paktika province that was filled at the time with militants arriving from Pakistan. Indications were that it had been in use for some time, perhaps several years, as a training camp and logistics hub.
