The U.S. government apologized on Wednesday for a helicopter attack that killed two Pakistani soldiers. According to a NATO investigation, the choppers crossed the border between Afghanistan and Pakistan several times before the Pakistanis fired warning shots to notify the choppers of their presence. The pilots, thinking they were being shot at, responded with a 25-minute barrage. If you're flying along in a helicopter, how can you tell whether you're in Afghanistan or Pakistan?
Sometimes it's impossible. With few indications of a border on the ground, helicopter pilots rely on GPS units, which indicate the boundary between the countries with a bright black line. If those systems fail, they have radar and paper maps. But these navigational tools are often of little use, since the border itself is in dispute. For the most part, Afghan maps are based on Russian cartography, while the Pakistani government relies on Raj-era British delineations. And many local people don't agree with either of them. U.S. forces have tried to refine their maps by asking tribal leaders where they think the border is located, but the process is slow and imperfect.
This situation is somewhat unique. Pilots working in South Korea have the benefit of a fence across much of the border. Many European countries have natural boundaries, like the Rhine River. Iran and Iraq have countless checkpoints. For most of the 1,519-mile border between Afghanistan and Pakistan, however, there's really no way to know which side you're on.
The Pakistan-Afghanistan border, such as it is, dates back to the late 19th century. In 1893, British Raj administrator Sir Mortimer Durand and Afghan amir Abdur Rahman agreed on a twisting, mostly arbitrary border that divided the Pashtun people between British India and Afghanistan. While Pakistan used the Durand Line as its official border on independence in 1947, Afghanistan has long argued that the line was only an agreement with the British, and that Pashtuns on the Pakistani side should have been given the option to join Afghanistan at the close of the Raj era. The Afghans have gone so far as to argue that the Durand Line was never a formal border in the first place but an informal frontier.
Before 2001, the border dispute didn't really matter because neither country policed the line. After the Sept. 11 attacks, however, the disagreement suddenly became relevant. The United States started demanding that Pakistan prevent militants from slipping across the unguarded border, and Pakistan complained about U.S. intrusions into their territory. Since 2002, a NATO-backed commission has been working to resolve the disagreement, but little progress has been made.
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Explainer thanks Lt. Col. John L. Dorrian of the International Security Assistance Force.