This chapter discusses how Sweden has relearned three lessons from the Cold War in light of ongoing transformations in its regional security environment. It compares and contrasts the security dynamics and policies of three distinct eras: the Cold War; the post-Cold War period; and the post-2014 period. It identifies changes in Sweden’s security environment that explain the timing and sequencing of those adaptations, discusses the basis for its ambiguous policy of neutrality during the Cold War, and why it contrasted from those of Denmark, Finland and Norway. It concludes that Sweden has relearned three lessons from the Cold War, i.e. that: (i) armed conflict on its territory will be associated with war on the Scandinavian Peninsula and in Finland; (ii) it needs realistic threat assessments in its defence planning; and (iii) it needs a concept of Total Defence to maintain the level of social resilience needed to discourage Russian attempts to attack, control or exploit its territory. While we often see the post-Cold War period as an anomalous gap in the history of Swedish security policy, this chapter establishes that Sweden’s process of abandoning its policy of neutrality in the 1990s actually serves as a strategic bridge in its ongoing implementation of an element of transparency in its security policy. In 2021, it became clear that if security on NATO’s northern flank were to deteriorate, Sweden would draw closer to NATO.