Although Pakistan allows Islamic terrorists to reside unmolested in North Waziristan, many of the Islamic radicals there do not return the favor. Thus, while Pakistan maintains a token garrison in Miranshah (the capital of North Waziristan), it requires a major military operation to run a weekly supply convoy (carrying mostly food and fuel) for the troops and officials there. The convoy must travel through over 70 kilometers of road that is normally controlled by Islamic terrorist groups (mainly the Pakistani Taliban). The terrorists plant many roadside bombs along the route and will attack any vehicles that will not submit to inspection. Since the military convoy is off-limits to such inspection, the movement of the convoy is an all-day affair and often involves violence or threats of violence.
Early in the morning army engineers start clearing the route of bombs and mines. This is usually done by noon, at which point the convoy and its armed guard proceed and, despite the occasional ambush, reach Miranshah by nightfall. The next day, the empty trucks must repeat the process to get back to their base at the town of Bannu. The Taliban could, if they wanted, cut off army access to Miranshah. But the army has made it clear that this would lead to massive use of artillery and air strikes. So the Taliban let the convoy pass with only light opposition. The government is allowed to do some other development work, like building or repairing roads, but with the understanding that these troops will not interfere with the Taliban and vice versa.
There are currently 150,000 troops in the Pakistani tribal territories, and nearly 40,000 are in or surrounding North Waziristan (an area of 4,700 square kilometers, with 365,000 people). North Waziristan has been surrounded since late 2009, but Pakistani generals have refused to go in and take down this terrorist refuge. Politicians have been under growing pressure from the West, especially the United States to do something about the continued terror attacks by what the Pakistanis call "bad Taliban". These are mostly Pakistani Taliban who want to establish a religious dictatorship in Pakistan. The Afghan Taliban, who wants to establish a similar government in Afghanistan are considered "good Taliban" (along with the minority of Pakistani Taliban who don't want to overthrow the government).
In the last two years, the Pakistani Taliban have also caused hundreds of casualties among pro-government tribesmen throughout the tribal territories, and it's no secret that the army hires tribesmen and puts them in dangerous situations to minimize army casualties. The army cannot afford to lose the support of the loyal tribes up there. All this has put pressure on the army to eliminate the refuge the killers can flee to in North Waziristan. Several times, because of the demands of Pakistani and American politicians, the Pakistani generals have said they will consider advancing into North Waziristan. But it hasn't happened yet. Meanwhile, the Pakistan army gets reminded how formidable the tribesmen can be as the troops run their weekly supply convoy to Miranshah.