Frederick William, known as the Great Elector, was the ruler of the {Brandenburg-Prussia} from 1640 until his death in 1688. He played a crucial role in strengthening the state during a time of political instability in the {Holy Roman Empire}. His leadership helped to consolidate power and expand the territory of his realm. He is best known for his military reforms and efforts to modernize the economy. Frederick William established a strong army and encouraged immigration to boost the population and workforce. His policies laid the groundwork for the future rise of {Prussia} as a major European power.