From Where is Osama bin Laden and Why Hasn’t He Been Caught?:
Waziristan is part of the Federally Administered Tribal Territories, an area roughly the size of Vermont. This 10,000 square miles of peaks and valleys set against the Hindu Kush Mountains is dotted with caves, tunnels and walled compounds, any one of which could be hosting the world’s most famous fugitive. This is the area that Osama bin Laden and several hundred al-Qaeda fighters escaped to after the battle of Tora Bora in January of 2002. With the assistance of extremists in Pakistan, they set up headquarters and training camps and operated freely for more than two years until the U.S. pressured Gen. Musharraf into mounting a military operation against them.
Tens of thousands of soldiers were sent in, paid for by the American government to crush al-Qaeda, kill or capture what was described as a “high value target,” and stop remnants of the Taliban from crossing into Afghanistan to attack American troops. The Pakistani Army was met with heavy resistance. The army says it has driven al-Qaeda from its base camps, but the enemy is still here. The terrain is not the only thing in Waziristan that’s unfriendly. The local Pashtoon tribesmen are Pakistani in name only. They have their own language and customs, and are governed by their own tribal laws. In fact, CIA Chief Porter Goss as much as said that he believed that bin Laden was hiding in the tribal territories in Pakistan, and was being protected by the Pakistani government.