The Kingdom of Prussia (German: Königreich Preußen) was a kingdom that constituted the state of Prussia between 1701 and 1918 and included parts of present-day Germany, Poland, Russia, Lithuania, Denmark, Belgium and the Czech Republic. It was the driving force behind the unification of Germany in 1871, and was the leading state of the German Empire until its dissolution in 1918. Although it took its name from the region called Prussia, it was based in Brandenburg, where its capital was Berlin. The kings of Prussia were Hohenzollerns. Prussia was a great power from the time it became a kingdom, through its predecessor, Brandenburg-Prussia, which became a military power under Frederick William, known as “The Great Elector”.