The attack began at roughly 2 a.m. local time. Two AH-64D Apache Longbow helicopters, an AC-130H Spectre gunship, and two F-15E Strike Eagle fighter jets crossed into Pakistani airspace, penetrating between 200 meters and 2.5 kilometers past the border. Their targets were two checkpoints perched on the Salala mountaintop, separated by about a kilometer. The first post, code-named "Volcano," sat at the peak. When the initial strike cut its communications, soldiers at the second post, "Boulder," opened fire on the helicopters with anti-aircraft guns. According to Pakistan's military, approximately 40 soldiers had been present at the two posts, most of them asleep. Among the dead were Major Mujahid Mirani and Captain Usman Ali. Pakistan insisted the assault continued for two hours, even after its officials alerted coalition forces to stop. NATO maintained it was returning fire.

The Afghanistan-Pakistan border, drawn by the British diplomat Sir Mortimer Durand in 1893, has never been a clean line on the ground. Taliban fighters routinely crossed it. Pakistani border posts sat in close proximity to Afghan territory. American officials pointed to a 2010 incident in which U.S. helicopters had struck a Pakistani outpost after insurgents used its position as cover. The working assumption among coalition forces, military officials in Kabul later explained, was that militants sometimes fired from empty Pakistani border bases. Pakistan rejected this framing entirely, calling the attack "unprovoked and indiscriminate," a "stark violation" of its sovereignty. The Pakistani military insisted there had been no militant activity in the area that night and challenged NATO to produce evidence of any fire originating from its side. The truth likely lies somewhere in the confusion inherent to combat along a poorly marked frontier, where friend and foe occupy overlapping terrain.

Pakistan's retaliation was immediate and strategic. The government shut down both NATO supply routes into landlocked Afghanistan: one through the Khyber Pass at Torkham and another through Balochistan near Chaman. The consequences were staggering. Pentagon figures from January 2012 showed the United States paying $104 million per month to route supplies through Central Asia, roughly $87 million more than the Pakistani routes had cost. The alternative Northern Distribution Network, threading through Russia, Kazakhstan, Uzbekistan, and Tajikistan, was longer, more expensive, and politically precarious. The closure also delayed delivery of thousands of armored vehicles intended for the Afghan army and police, slowing the very force-building that was supposed to enable American withdrawal. Pakistan had turned geography into leverage.

For months, negotiations snagged on a single demand. Pakistan wanted an apology. The United States refused, partly on principle and partly because American military investigators concluded that Pakistani soldiers had fired first. Pakistan demanded $5,000 per supply truck as a reopening fee; the U.S. called that unaffordable. Diplomatic meetings stalled. A hoped-for breakthrough at the 2012 NATO Chicago Summit never materialized. Then, on 3 July 2012, Secretary of State Hillary Clinton telephoned Pakistani Foreign Minister Hina Rabbani Khar. "We are sorry for the losses suffered by the Pakistani military," she said. Pakistan dropped its demand for the higher transit fee, keeping the rate at $250 per truck. The Obama administration agreed to ask Congress to reimburse Pakistan roughly $1.2 billion for counterinsurgency costs along the border. The supply lines reopened. But the damage extended far beyond shipping fees.

The Salala incident left marks that no apology could erase. Pakistan expelled American personnel from Shamsi Airfield in Balochistan, the only U.S. military base on Pakistani soil, completing the evacuation by 11 December 2011. The Pakistani flag replaced the American one. Army chief General Ashfaq Parvez Kayani ordered border commanders to fire without waiting for permission if any further incursion occurred, and Pakistan deployed Anza Mk-III shoulder-fired missiles and anti-aircraft guns along the frontier. The Pakistan Air Force began round-the-clock combat air patrols over the border. Pakistan boycotted the Bonn Conference on Afghanistan, diminishing that gathering's effectiveness. The country halted its facilitation of U.S. negotiations with the Afghan Taliban. The total cost of the supply line closure exceeded one billion dollars. "It was a matter of honor for the army," a Pakistani defense journalist explained. "The only word they were looking for was 'sorry.'" That word, when it finally came, bought a reopened road but not a repaired relationship.