9. The Kosovo War (1998-1999)
The Kosovo War, spanning from February 1998 to June 1999, was marked by intense ethnic conflict between Kosovo Albanians and Serbian forces. In response to escalating violence and humanitarian concerns, NATO initiated Operation Allied Force on March 24, 1999, commencing a 78-day air campaign against the Federal Republic of Yugoslavia (nato.int). Notably, this intervention proceeded without a formal declaration of war, raising significant debates regarding international law and the legitimacy of humanitarian interventions.
