A defense alliance is a strategic partnership between nations in which they agree to provide military support to each other in the event of war. Collective defence is at the heart of the Alliance – an attack against any one member is considered to be an attack against all members, as reflected in Article 5 of NATO’s founding Washington Treaty.
Allies are strengthening the Alliance’s deterrence and defence posture to address an increasingly complex threat environment. This includes a comprehensive response to Russia’s campaign of aggression and coercion. The Alliance’s efforts to adapt include stepping up defence spending and modernising capabilities. It also includes a whole-of-society approach to defence and security, including civil preparedness and countering hybrid threats.
At the 2023 Vilnius Summit and 2024 Washington Summit, Allied Leaders agreed significant measures to enhance NATO’s readiness and capabilities, particularly in the Alliance’s eastern flank. They also strengthened NATO’s ability to rapidly reinforce any Ally that is threatened. This is the most significant reinforcement of NATO’s collective defence in a generation.
At the same time, Allies have increased defence investments and taken steps towards fairer burden-sharing in NATO. At the 2025 NATO Summit in The Hague, Allied Leaders committed to invest at least 5% of their GDP in defence by 2035. This will enable Allies to meet NATO’s capability targets and ensure that they have the forces, capabilities, infrastructure, resources, warfighting readiness and resilience required to deter and defend. This also enables them to continue investing in innovation and defence industrial development, helping the Alliance to maintain its decisive military edge in the future.