The North Atlantic Treaty Organization is undergoing a profound change. At the Madrid summit in July 2022, the alliance ratified a new strategic concept that returned NATO to its roots: deterring Russian aggression. At that same meeting, NATO began the process of welcoming Sweden and Finland into the alliance, leading to Finland’s full accession in April 2023. At the Vilnius summit this past summer, NATO continued to adapt in response to Russia’s war on Ukraine. The alliance updated its military plans and established the NATO-Ukraine Council. It also eased Ukraine’s path to accession by announcing that it could join the alliance without completing a membership action plan (MAP).One hundred days after Vilnius, as the alliance begins its preparations for its seventy-fifth summit next year in Washington, join Hudson’s Peter Rough and Luke Coffey as they welcome two Lithuanian national security experts for a retrospective analysis of the Vilnius summit: Žygimantas Pavilionis, a member of the Seimas (Lithuania’s parliament), where he serves on the Committee of Foreign Affairs, and Tomas Janeliūnas, the chief research officer at the Eastern Europe Studies Centre and a professor at Vilnius University.