Charles X Gustav was the King of Sweden from 1654 until his death in 1660. He belonged to the House of Palatinate-Zweibrücken and was known for his military leadership during the Second Northern War. His reign was marked by efforts to strengthen Sweden's position in Europe and expand its territories. During his rule, Charles X Gustav initiated the Swedish Empire's military campaigns, notably the invasion of Poland and the Treaty of Copenhagen in 1660. His ambitious policies aimed to enhance Sweden's influence, but his reign ended abruptly with his untimely death, leaving a mixed legacy in Swedish history.