Over the past quarter-century, northern Europe has been transformed. Formerly riven by Cold War divisions, today the region shows that market democracy can work, human rights and the rule of law can be respected, a positive outward vision of the world is still possible, and the transatlantic cooperation remains indispensable to tackle many challenged. Yet insecurities have yet again returned to northern Europe, and greater uncertainties also beset the High North, with its shared borders and special neighborhood. The Center for Transatlantic Relations has brought together strategists and experienced practitioners from many different countries to explore ways to advance U.S.-Nordic-Baltic security cooperation in light of changing security challenges facing the transatlantic community. Authors explore integrated approaches to preventive diplomacy and security, alternative NATO partnership architectures and energy security. They examine U.S-Nordic-Baltic cooperation on the Arctic and the High North. They suggest ways to strengthen U.S.-Nordic-Baltic defense cooperation and recommend more effective ways to realize a Europe whole, free, and at peace, particularly in light of Russia's continued provocations in central and northern Europe.