Since the end of the cold war, Estonia, Latvia, and Lithuania have been confronted with four major milestones that necessitated the cardinal transformation of their national security and defence policies: the collapse of the Soviet Union, NATO membership, EU accession, and the resurgence of Russia under Putin. This chapter analyses the countries’ responses to these changes and challenges, tracing and explaining the evolution of Estonian, Latvian, and Lithuanian national strategies, military doctrines, and capabilities since 1989. It both provides an analytical overview of how the countries collectively have adjusted to the new regional and international security order, as well as compares the similarities and differences in their security outlooks, postures, and actions, in order to shed light on the degree of convergence and divergence among these three post-communist states.