This article addresses the changing security environment in the Baltic Sea region and reviews the patterns of cooperation and conflict since the end of the Cold War. The exploration starts from the concerns voiced by analysts since 2014 that the Baltic Sea could become the scene for a military confrontation with Russia. The article reviews the scholarly debates and examines the insights gained from past developments in the region. It underlines the utility of cooperation to address emerging security challenges and highlights the drivers of insecurity and threat perceptions, revealing the importance of changes in the sense ofidentity and belonging across the region. The article situates the contributions to the Forum -- The Return of Geopolitics to the Baltic Sea Region -- in the context of the lessons that can be drawn from the shifts and changes that have taken place in the region in the last three decades.