Twenty-five years of relative calm and predictability in relations between Russia and the West enabled European governments largely to neglect their military capabilities for territorial defense and dramatically redraw Northern Europe's multilateral, regional, and bilateral boundaries, stimulating new institutional and cooperative developments and arrangements. These cooperative patterns of behavior occurred amid a benign security environment, a situation that no longer obtains. Following Russia's annexation of Crimea, its military incursion into eastern Ukraine, its substantial military modernization efforts, heightened undersea activity in the North Atlantic and Baltic Sea, and its repeated air violations, the region's security environment has dramatically worsened. The Baltic Sea and North Atlantic region have returned as a geostrategic focal point. It is vital, therefore, that the United States rethink its security approach to the region—what the authors describe as an Enhanced Northern Presence.