The U.S. State Department recently concluded a four year investigation of one of its contractors in Afghanistan. The subject was paying bribes to Pakistani officials to get people and equipment from the port of Karachi and into landlocked Afghanistan. The investigation concluded without recommending the contractor be punished. That’s because such bribes are a way of life in Pakistan and any foreign government operating there knows that you cannot get anything done without paying bribes. The American investigation did not find any fraud on the part of the American contractor (like their employees stealing bribe money) thus there was no crime according to U.S. law. Many Americans think that U.S. law forbids the paying of bribes overseas. In fact, the law does not do this in all instances. When you have a situation, as in Pakistan, where you simply cannot get things done without paying bribes, then that is, according to American law, legal. The U.S. government prefers that this sort of thing be done discreetly and without attracting investigations like this.
The situation with Americans in Pakistan is all because Afghanistan is landlocked and most imports and exports move along the 1,600 kilometers long truck route from Kabul to the Pakistani port of Karachi. Only a few hundred kilometers of the route (mostly National Highway 55 in Pakistan) is a proper, multilane road common in the west. The rest of it, especially in the Pushtun territories astride the border, is a poorly maintained and quite narrow two lane road, often twisting its way up and down mountains. The Pushtun tribes on both sides of the Afghan-Pakistan border, in cooperation with government officials on both sides of the border, demand additional payments from trucking companies if they want their trucks to get across the border and into Afghanistan intact. That has cost Afghanistan and the foreign countries trying to help Afghanistan billions of dollars in additional transportation costs because of the bribes plus the costs of lost or damaged cargo. All this is nothing new.
For centuries, the tribes along this route collected payments from the merchants (or, these days, trucking companies) to insure safe passage. Some of the current tribes are pro-Taliban, but this is business, and it has become more lucrative as the Afghan economy has revived since 2001 (when the reactionary, and bad for business, Taliban were chucked out). But as the Pushtun tribes split into pro and anti-Taliban groups, one of the side effects was a struggle over who would control the "security" business on the roads into Afghanistan. This explains the occasional attacks made on convoys and truck stops. While you hear about the U.S. and NATO convoys being attacked, the battles back in the hills, between the rival warlords, gets less coverage (mainly because reporters are apt to be shot, just to keep the media away from the savage fashion in which these disputes are settled.) The truck security payments (often several thousand dollars or more per truck per trip) are a major source of cash for the border tribes. It's something worth fighting, and dying, for. At the height of the trucking activity (2006-2010), the cost of getting a truckload (usually just a large cargo container) from Karachi to Kabul went from a thousand dollars to nearly $3,000. During that period over 5,000 trucks were destroyed and at least 120 drivers killed anyway. But only about one percent of NATO shipments were lost. It’s the Afghan economy as a whole which suffers the most.
While religion and tribal politics play a big role in the Taliban and al Qaeda violence in Pakistan and Afghanistan, you also have to follow the money to get to the source of most of the fighting. You can live without religion, but you can't live without food. And that will cost you, especially in one of the poorest regions of Asia. It's also one of the most heavily armed parts of Asia, where hungry tribesmen have long resorted to violence when they were hungry, or just greedy.
U.S. and NATO commanders soon got fed up with the "protection" scam being run them on the supply route. In response, NATO has been bringing more cargo in via Russian and Central Asian railroads (the old Soviet rail network). This has been increasing since 2010 and made a noticeable dent in traffic going through the Khyber pass. That meant most of the traffic still being threatened moving through Pakistan was for the Afghan economy. Thus more civilian traffic is also shifting to the rail lines coming to the Afghan border via Central Asia. For the first time, some railroads are being built in Afghanistan. There were limits on how much traffic could be shifted north. For one thing there were few good roads going from north to south (where most of the fighting was) and there was one tunnel (the Salang) that carried more traffic than it was designed to. Salang was the quickest way south and has been a real bottleneck. So Pakistan still gets all this traffic, and a license to steal from the truckers.