The Prussian kings were the rulers of the Kingdom of Prussia, which emerged in the early 18th century. The most notable among them was Frederick II, also known as Frederick the Great, who reigned from 1740 to 1786. He is remembered for his military successes and efforts to modernize Prussia, turning it into a major European power. The Prussian monarchy played a significant role in the unification of Germany in the 19th century. Under the leadership of Otto von Bismarck, the Prussian kings helped establish the German Empire in 1871, with the King of Prussia becoming the German Emperor. This marked a pivotal moment in European history.