King Charles XII was the King of Sweden from 1697 until his death in 1718. He became king at a young age and is known for his military leadership during the Great Northern War, where Sweden fought against a coalition of countries including Russia, Denmark-Norway, and Saxony. His reign was marked by significant battles, including the famous Battle of Narva in 1700. Despite his early successes, Charles XII faced challenges as the war dragged on. He spent several years in exile in Turkey after a defeat and returned to Sweden to continue his efforts. His ambitious campaigns ultimately led to Sweden's decline as a major power in Europe.