NATO's Article 5 collective defense clause has remained uninvoked since its sole historical activation after the 2001 terrorist attacks, as no armed assault has struck alliance territory amid the Russia-Ukraine conflict or other regional tensions through mid-2026. Traders assign a 91.5% implied probability against invocation before 2027, reflecting sustained NATO deterrence measures including eastern flank reinforcements, joint exercises, and weapons support for Ukraine that stops short of direct combat involvement. This positioning aligns with the alliance's emphasis on Article 4 consultations for incidents like airspace violations, while avoiding escalation thresholds that could prompt North Atlantic Council consensus on full collective defense. Ongoing diplomatic channels and capability enhancements further reduce near-term risks of the triggering conditions required for resolution.