The history of Prussia seems to start sometime around the 1220s with the attempt to conquer the Prussian tribes of the Baltic, in a region covered by parts of modern day Poland, Russian, and Lithuania. In the process, an independent state was created under the control of the Teutonic Knights, which continue to grow until conflict was initiated by an alliance of Poland and Lithuania. The Teutonic Knights lost and the Western part of Prussia was ceded to Poland in 1466. In 1525 the remaining parts of Prussia became the first Protestant state in Europe, though it still had ties to Poland. In 1701, it was reorganised as a Kingdom under the leadership of Elector Frederick III, who renamed himself "King Frederick I of Prussia". It was his son, Frederick William I who started the habit of expanding the Kingdoms' borders. In the 1740s Prussia emerged as one of Europes great powers under King Frederick II,
It was the twin battles of Jena and Auerstedt fought on October 14, 1806 that finally changed the fortunes of Prussia. In those battles, the Prussian Monarchy had fought against the forces of Napoleon Bonaparte of France, and lost. The Treaties of Tilsit in 1807 resulted in Prussia losing half of its territory, much of it to the Duchy of Warsaw. It was not until Napoleons defeat at Waterloo in 1815, that Prussia got most of its lost territory. In exchange for giving up more of Polands territory, Prussia was given the Rhineland, Westphalia, the Ruhr area, and other parts of the Germanic areas.
Under the leadership of Prime Minister Bismarck, Prussia eventually brought the unification of Germany in 1870 in the form of the German Empire. After the dismissal of Bismarck in 1890, Emperor William II of the German Empire led a militarization of the Empire. That in turn led to the disaster of World War I, and subsequent German Revolution of 1918. After which William II abdicated both as Emperor of the German Empire and as King of Prussia. Prussia was subsequently converted to a free state within the Weimar Republic of Germany.