On September 30, NATO helicopters killed two and injured four soldiers from Pakistan's paramilitary organization, the Frontier Corps (FC), when NATO aerially attacked the FC border post within Kurram agency. According to NATO's command in Kabul, two ISAF helicopters were pursuing insurgents from the Afghan side of the border. Curiously, the Frontier Corpsmen thought it would be prudent to issue "warning shots" when the helicopters entered Pakistani airspace. Unfortunately, the NATO helicopter crew shot two rockets in self-defense. NATO claims that the FC troops were mistaken for militants and that the tragedy could have been avoided had there been better coordination between NATO and Pakistan's military. A similar situation occurred in June of 2008; however, in that case the innocence of the soldiers remains very much in dispute with the Department of Defense insisting it was a legitimate action against a hostile target.

Within hours of last Thursday's helicopter strikes, the Pakistani government retaliated by shutting down the Torkham border crossing, which lies north of Peshawar on the Grant Trunk Road. Torkham is the crossing through which a majority of non-lethal NATO supplies pass into Afghanistan from Pakistan, once they are offloaded from ships based in Pakistan's port city of Karachi. The other main crossing into Afghanistan, at Chaman linking Baluchistan and Kandahar, has remained open.

With the closure at Torkham, transport vehicles and their Pakistani drivers became sitting targets for insurgent attacks as the trucks continued to pile up, unable to move forward. The Pakistani Taliban, vexed by the enduring successes of the drones that target them and their allies, vow that they will shut down the NATO supply route and have set more than 120 NATO vehicles on fire. Many of the drivers, who are Pakistani, have been killed. Many more are likely considering finding a safer way to earn a living.

The government's retaliatory closure of Torkham and the ensuing violence against the trucks have discomfited Af-Pak watchers who worry about Pakistan's important source of leverage over the United States and NATO. Some analysts worry that Pakistan will deploy its ultimate -- and only -- weapon as an effort to seek concessions on the end state in Afghanistan or to extract even greater funds from the international community.

Indeed, NATO and the United States have tried to free themselves in some measure from their nearly exclusive dependence upon Pakistan by developing a northern supply route through the Central Asian states. Those have yet to come to fruition for a number of diplomatic, political, and frankly logistical concerns. And while Iran has a suitable port in Chahbahar that is connected by road to Afghanistan, few would seriously entertain that as an option due to enduring problems with Iran regarding nuclear proliferation and terrorism. The deep sea port at Chahbahar is connected via roads to the Afghan border and onward to Afghanistan's Ring Road. Both the port and the road network linking the port to Afghanistan was built with Indian assistance.

As I have noted previously, this position is puzzling. Pakistan has a longer history in terms of proliferation and state support for terrorism than does Iran, yet Washington has funneled nearly $19 billion into Pakistan since September 11, 2001 in recognition of Pakistan's primacy to U.S. security interests. Even if the United States were to act in its own strategic self interests and pursue a tactical arrangement with Iran over the port, no doubt Iranian President Mahmoud Ahmadinejad would not miss the opportunity to miss an opportunity to productively engage the international community.

While the anxiety surrounding the road closures that attract attacks is understandable, the real puzzle is not how to prevent these outcomes generally or even why this one happened in particular. The real question is why doesn't this happen more often and with greater consequence? Even garden variety pilferage of the supply line is minimal according to U.S. officials and this current episode has been a nuisance but not a strategic threat. The 120 or more trucks that have been destroyed comprise less than one percent of the total traffic in any given month, according to U.S. Department of Defense officials.

So, why haven't attacks on the supply line to Afghanistan been more common? It's reasonable to argue that a dedicated and sensible insurgent would target these trucks along the way from Karachi to Torkham or to Chaman in Pakistan and from Torkham or Chaman to their final destinations within Afghanistan. This would be simple to do as the Pakistani security forces do not protect those privately-owned trucks and much of the route in Afghanistan winds through narrow mountain passes.

The answer is simple: trucking mafias and organized criminal and insurgent networks are all making money off of this system. The system of payoffs is elaborate yet elegant. Pashtuns dominate the trucking mafia in Pakistan and represent enormous financial interests in the fundamental integrity of the supply line system. The drivers and their companies must pay off Pakistani police and any other relevant government officials to secure "safe" passage and to resolve any "paperwork complexities."

Insurgents and criminal organizations also get their courtesy payment in exchange for safe passage to Afghanistan. Ordinary smugglers and blackmarketeers get their pieces of the pie too. Cargo containers are pilfered in small amounts. They are in turn auctioned off and the buyers sell their contents in the "bara bazaars" (black markets) throughout Pakistan. Some of the contents of the trucks have made their way into the hands of Pakistani insurgents. Overall, pilferage is low. This seems deliberately calibrated to ensure that such loss is an irritant to be tolerated rather than a problem to be fixed.

Trucks have been torched in the past and sometimes in large number. But it is not as it appears in all instances. While I was with the United Nations Assistance Mission in Afghanistan in 2007, I travelled to Jalalabad to meet UNAMA staff there. They explained that time-tested insurance scams are an easy way for Pakistani drivers and their employers to make cash. Trucks coming to Afghanistan offload their fuel in Pakistan at an appropriate price. Then, with only a minimal amount of fuel, the truck is "attacked" and "set on fire." The company files an insurance claim for both the lost truck and the value of the lost cargo. It is almost impossible to say how often this takes place. Sometimes it can backfire: with dozens of trucks lined up bumper to bumper, when one truck catches fire there is a deadly domino effect.

When trucks enter Afghanistan, various local "security firms" are entrusted with the responsibility that these goods meet their destination. As is well known and as detailed in a recent report by the Senate Armed Services Committee, these firms also make handsome contributions to the Afghan Taliban and other nefarious state and non-state actors.

So how will this current kerfuffle end? Pakistan will remind the United States that Pakistan is indeed important. The United States will remind Pakistan that it needs U.S. cash to keep its wrecked economy afloat and that its security assistance is tied to demonstrated assistance in the war on terror, aiding -- not undermining -- U.S. efforts in Afghanistan among other requirements stipulated in the Kerry-Lugar-Berman aid bill. Washington may even find "accounting" or other problems with Pakistan's numerous requests for Coalition Support Funds reimbursement. These procedural glitches can likely be resolved with an open road and safe passage. Indeed, the Pakistani Army will no doubt signal its appreciation of the "strategic value" of its relations with the United States and persuade the bureaucracy to open the road by early next week if not sooner. And once the road opens, the trucks will be less vulnerable.

However, the problem of torching tankers is not entirely within the hands of Pakistan's security forces. And this challenge is beyond the ability of NATO or the United States to influence.

Sooner -- rather than later -- the mafias and the militants will want their revenue streams reopened. To get the trucks rolling, there will be a slew of renegotiated contracts with trucking firms and protection rackets demanding a higher price to get the job done. The drivers -- who make the least off of this racket -- will also likely see increased pay in recognition of the increasing dangers of the task. In the end, the loss of profit to all parties during this last week will be recouped in spades when the traffic resumes at higher prices.

It is the non-state actors who will likely decide when enough is enough and get the traffic and their profits moving again. And they will again decide when it's time to renegotiate their contracts by blowing up more trucks.

Christine Fair is an assistant professor at Georgetown University and the author of Cuisines of the Axis of Evil and Other Irritating States.