This article critically examines, from the perspective of Articles 51 and 42 of the UN Charter, the legal frameworks underlying the U.S. invasion of Afghanistan and NATO's humanitarian intervention. It reviews the justification for the US-led invasion in reaction to the 9/11 attacks as an act of self-defense that appraises NATO's ensuing involvement under UNSC resolutions and the prevailing parameters of international law. The study delves into the origins of the 20-year conflict, with a focus on the tragedy of September 11 as the catalyst for the prolonged war. In particular, this analysis examines the complicated process of foreign troops drawdown, highlighting the impact of the Doha Agreement and the extended timeline set by the United States, which have exacerbated Afghanistan's economic and political upheavals. This analysis aims to illustrate the complex relationship between international law and geopolitical dynamics, with a particular focus on the legal and humanitarian dimensions of military intervention.
