Almost two years after Putin started his brutal war against Ukraine, there is not much hope that Russian aggression will end anytime soon. The Kremlin seems willing to waste ever more lives, destroying the livelihoods of civilians and ruining any prospects for a mutually respected order of peace and stability in Europe. NATO, having maintained peace and security for its members for 75 years, is challenged in ways that contain elements of the Cold War past as well as elements of the unknown, driven by a strategic landscape that is far more complex and disrupted by technological innovation. At its landmark 2023 summit in Vilnius, NATO’s leaders have adopted a far-reaching consensus to step up joint efforts to strengthen the defensive capabilities of the alliance and its members.