This is a question that calls for a judgment of values rather than a factual claim that can be settled by searching—reasonable, well-informed people disagree sharply on it, and the "right" answer depends on political, historical, and moral premises that aren't resolved by evidence alone. Rather than giving you my own verdict, let me lay out the main considerations on different sides so you can weigh them yourself.
Arguments that NATO is a force for good:
•Deterrence and peace in Europe: Supporters argue NATO's collective defense (Article 5) deterred Soviet aggression during the Cold War and has prevented major war between great powers in Europe for over 70 years.
•Stability and democratic anchoring: NATO membership is often credited with helping consolidate democracy and civilian control of the military in post-Communist Eastern Europe (e.g., Poland, the Baltic states).
•Response to Russian aggression: Many argue NATO's existence and expansion have been a necessary defensive response to Russian actions, including the invasions of Georgia (2008) and Ukraine (2014, 2022).
•Burden-sharing and multilateralism: It's framed as a rules-based alternative to unilateral action, pooling resources among democracies.
Arguments that NATO is harmful or not clearly a force for good:
•Provocation thesis: Critics (including some realist scholars like John Mearsheimer) argue NATO expansion eastward after the Cold War needlessly antagonized Russia and contributed to the conditions for conflict, including the war in Ukraine.
•Military interventions: NATO's bombing campaigns—Kosovo (1999) without UN authorization, and especially Libya (2011)—are criticized for causing civilian harm and, in Libya's case, contributing to state collapse and prolonged chaos.
•Democratic legitimacy concerns: Some argue NATO entrenches U.S. military dominance over European foreign policy and reduces European strategic autonomy.
•Opportunity costs: Critics on the left and some libertarians argue NATO memberships lock countries into high military spending and alliance obligations that might not reflect their own populations' interests.
Where the disagreement really lies:
Much of the debate boils down to differing theories of international relations—realists emphasizing spheres of influence and the dangers of alliance expansion, versus liberal internationalists emphasizing the value of collective security and democratic solidarity. It also depends on how you weigh specific historical episodes (Kosovo, Libya, Ukraine) and whose perspective (Eastern European states that sought NATO protection vs. Russia's stated security concerns) you prioritize.
If you want, I can go deeper into any specific piece of this—like the debate over NATO expansion and Russia, or the Libya intervention's aftermath—where I can pull in more specific historical detail.