Charles XII was the King of Sweden from 1697 until his death in 1718. He became king at the young age of 15 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 years in exile after a defeat at the Battle of Poltava in 1709, eventually returning to Sweden. His ambitious military campaigns ultimately led to the decline of the Swedish Empire.