Following the wars in the Balkans, the North Atlantic Treaty Organization (NATO) and the International Criminal Tribunal for the former Yugoslavia (ICTY) established solid cooperation, whereby NATO supported ICTY in its quest to bring persons indicted for war crimes (PIFWCs) to justice. NATO Headquarters has provided substantial material used as evidence in various ICTY cases. NATO members have participated as witnesses to ICTY. Personnel of the NATO-led operations in Bosnia and Herzegovina, as well as Kosovo, have detained and handed PIFWCs over to ICTY personnel who arrested them based on indictments issued by the tribunal's prosecutor. The solid working relationship, while possibly temporarily challenged, was not put in serious jeopardy when the ICTY prosecutor investigated NATO's conduct of operations during Operation Allied Force (also known as the Kosovo Air Campaign). The investigation did later clear NATO of the allegations of war crimes levied against it.