One of the largest states in Europe and the greatest of the Protestant powers, Denmark, in the 16th and 17th centuries was at the height of its influence. Embracing Norway, Iceland, portions of southern Sweden, and northern Germany, the Danish monarchy dominated the vital Baltic trade. However, its geopolitical importance far exceeded its modest resources. This book examines the short and perhaps unlikely career of Denmark as the major power of northern Europe, exploring its rise to the forefront of European affairs and its subsequent decline in fortunes following its disastrous involvement in the Thirty Years' War. The book focuses on key issues, from the dynamic role of the Oldenburg monarchy in bringing about Denmark's 'European integration', to the impact of the Protestant Reformation on Danish culture. The multi-national character of the Danish monarchy is explored in-depth, in particular how the Oldenburg kings of Denmark sought to establish their authority over their sizable - and oftentimes contentious - Norwegian, Icelandic, and German minorities. Denmark's participation in international politics and commerce is also investigated, along with the power struggle between Denmark and its rival Sweden over Baltic dominion, and the Danes' unique approach to internal governance.