King Frederick IX was the King of Denmark from 1947 until his death in 1972. Born on March 11, 1899, he was the son of King Christian X and Queen Alexandrine. Frederick IX played a significant role in modernizing the Danish monarchy and was known for his approachable demeanor and love for music, particularly classical music. During his reign, Denmark experienced significant social and political changes, including the establishment of a welfare state. Frederick IX was also a naval officer and served in the Royal Danish Navy. He was succeeded by his daughter, Queen Margrethe II, who became the first female monarch of Denmark since the Middle Ages.