German rulers have played a significant role in shaping the history of Germany and Europe. From the early medieval period, leaders like the Holy Roman Emperors governed vast territories, often uniting various German states under a single crown. The Prussian kings, particularly in the 19th century, were instrumental in the unification of Germany, leading to the establishment of the German Empire in 1871. The role of German rulers evolved over time, with the decline of monarchies after World War I. The Weimar Republic replaced the imperial system, and later, the rise of the Nazi regime marked a dark chapter in German history. Today, Germany is a federal republic, with no ruling monarch.