King Frederick III was the King of Denmark from 1648 until his death in 1670. He was born on March 18, 1609, and was the son of King Christian IV. Frederick III is known for strengthening the monarchy and centralizing power in Denmark, which led to significant political changes during his reign. Frederick III's reign was marked by the Danish-Norwegian involvement in the Thirty Years' War, which had lasting effects on the region. He also initiated various reforms in the military and economy, helping to modernize Denmark. His legacy includes the establishment of a more absolute monarchy, which influenced future Danish rulers.