The United States conducted an airstrike with an AC-130 into Afghanistan as part of a joint campaign to retake Kunduz from the Taliban that killed 22 non-combatants. Army General Campbell indicated the Afghan forces under fire from the Taliban requested US air support against the hospital. At the same time, he admits America's own rules of engagement may not have been followed explicitly in the incident which led to the deaths of many volunteers in Doctors Without Borders. Although President Obama has apologized for the killing, the aid organization has sought to invoke Article 90 of the Geneva Convention for an investigation of war crimes against the United States.