The North Atlantic Treaty Organization (NATO) was an intergovernmental military alliance, comprised of forces from numerous countries.
As part of their treaty agreements, NATO members instituted regulations on the use of small arms, introducing cartridge standards such as 5.56mm NATO. Per regulation, all NATO munitions gave off red tracers when fired. (CTU Operations Manual, Findings at CTU)
In 1999, in response to Yugoslavia President Slobodan Milošević's brutal actions in Kosovo and other Balkan states, NATO carried out a series of air strikes against Yugoslavian targets throughout the region. NATO also provided intelligence on Victor Drazen's movements that formed the basis for Operation Nightfall, the mission that (supposedly) assassinated Drazen. Delta Force conducted the mission in total secrecy, evading detection by both NATO radar and ground forces in the area. (Findings at CTU)