The geopolitical environment of the Baltic Sea is rapidly changing. This has complex implications for the national security of Sweden and Finland, the only Scandinavian countries that are not members of NATO. Although Sweden and Finland have military cooperation, the question is whether this partnership is sufficient in times of instability. From a historical perspective, Swedish-Finnish military relations have been complicated. However, today Sweden and Finland might have a mutual interest in the field of regional security. Is NATO membership the right move for Sweden and Finland or would enhanced Swedish-Finnish military cooperation be a better option? As the debate continues, Sweden and Finland are targets of Russian propaganda and hybrid warfare. Are Sweden and Finland prepared for a new way to wage war? These issues are addressed in Finland and Sweden - Partners with a Mutual Interest?, an anthology of essays by prominent scholars, defence force representatives, diplomats and politicians. The essays are based on lectures given at a seminar arranged by the Axel and Margaret Ax:son Johnson Foundation on 22 January 2016 in Helsinki, Finland.