In a friendly-fire incident, a skirmish occurred between U.S.-led NATO forces and Pakistani security forces at two military checkposts along the Afghanistan–Pakistan border.

In military terminology, friendly fire or fratricide is an attack by belligerent or neutral forces on friendly troops while attempting to attack enemy or hostile targets. Examples include misidentifying the target as hostile, cross-fire while engaging an enemy, long range ranging errors or inaccuracy. Accidental fire not intended to attack enemy or hostile targets, and deliberate firing on one's own troops for disciplinary reasons is not called friendly fire, and neither is unintentional harm to civilian or neutral targets, which is sometimes referred to as collateral damage. Training accidents and bloodless incidents also do not qualify as friendly fire in terms of casualty reporting.

The 2011 NATO attack in Pakistan was a border skirmish that occurred when United States-led NATO forces engaged Pakistani security forces at two Pakistani military checkposts along the Afghanistan–Pakistan border on 26 November 2011, with both sides later claiming that the other had fired first. Two NATO Apache helicopters, an AC-130 gunship and two F-15E Strike Eagle fighter jets entered as little as 200 metres (660 ft) to up to 2.5 kilometres (1.6 mi) into the Pakistani border area of Salala at 2 a.m. local time. They came from across the border in Afghanistan and opened or returned fire at two Pakistani border patrol check-posts, killing 28 Pakistani soldiers and wounding 12 others. This attack resulted in deterioration of relations between Pakistan and the United States. The Pakistani public reacted with protests all over the country and the government took measures adversely affecting the American exit strategy from Afghanistan, including the evacuation of Shamsi Airfield and closure of the NATO supply line in Pakistan. Pakistan also rejected a U.S. offer of compensation for the killing of its soldiers in the NATO attack.

The North Atlantic Treaty Organization, also called the North Atlantic Alliance, is an intergovernmental military alliance between 32 member states—30 in Europe and 2 in North America. Founded in the aftermath of World War II, NATO was established with the signing of the North Atlantic Treaty in 1949. The organization serves as a system of collective security, whereby its independent member states agree to mutual defence in response to an attack by any external party. This is enshrined in Article 5 of the treaty, which states that an armed attack against one member shall be considered an attack against them all.