He left the country three years later to embark on a series of battles overseas. These battles were part of the Great Northern War and many of them were fought against Peter I of Russia. Saxony, Denmark-Norway, Poland and Russia joined in a coalition to attack Sweden, starting what would later be known as the Great Northern War.
Charles XII was a skilled military leader and tactician. However, his skills as a politician in making peace were lacking. Charles is quoted by Voltaire as saying upon the outbreak of the Great Northern War, "I have resolved never to start an unjust war but never to end a legitimate one except by defeating my enemies." Although Sweden achieved several large scale military successes early on, and won the most battles, the Great Northern War eventually ended in Sweden's defeat which led to downfall of the Swedish Empire.
We Charles, by the Grace of God of the Swedes, the Goths and the Vends King, Grand Duke of Finland, Duke of Estonia and Karelia, Lord of Ingria, Duke of Bremen, Verden and Pommerania, Prince of Rügen and Lord of Wismar, and also Count Palatine by the Rhine, Duke of Bavaria, Count of Zweibrücken-Kleeburg, as well as Duke of Jülich, Cleve and Berg, Count of Waldenz, Spanheim and Ravensberg and Lord of Ravenstein
Charles's first campaign was against Denmark-Norway, ruled by his cousin Frederick IV of Denmark, which threatened a Swedish ally, Charles' brother-in-law Frederick IV of Holstein-Gottorp. For this campaign Charles secured the support of England and the Netherlands, both maritime powers concerned about Denmark's threats to close the Sound. Leading a force of 8,000 and 43 ships in an invasion of Zealand, Charles rapidly compelled the Danes to submit to the Peace of Travendal in August 1700, which indemnified Holstein.
Having defeated Denmark-Norway, King Charles turned his attention upon the two other powerful neighbors, King August II of Poland (cousin to both Charles XII and Frederick IV of Denmark-Norway) and Peter the Great of Russia, who also had entered the war against him.
Russia had opened their part of the war by invading the Swedish-held territories of Livonia and Estonia. Charles countered this by attacking the Russian besiegers at the Battle of Narva. The Swedish army of ten thousand men was outnumbered four to one by the Russians. Charles attacked under cover of a blizzard, effectively split the Russian army in two and won the battle. Many of Peter's troops that fled the battlefield drowned in the Narva River, and the total number of Russian fatalities reached about 17 000 at the end of the battle, while the Swedish troop lost 667 men.
Charles did not pursue the Russian army. Instead, he then turned against Poland-Lithuania, which was formally neutral at this point, thereby disregarding Polish negotiation proposals supported by the Swedish parliament. Charles defeated the Polish king Augustus II and his Saxon allies at the Battle of Kliszow in 1702 and captured many cities of the Commonwealth. After the deposition of the king of the Polish-Lithuanian Commonwealth, Charles XII put Stanisław Leszczyński on the throne.
Peter the Great defeated Swedish forces near the Baltic coast before Charles could combine his forces, and Charles' Polish ally, Stanisław Leszczyński, was facing internal problems of his own. Charles expected the support of a massive Cossack rebellion led by Mazepa in Ukraine but the Russians destroyed the rebel army before they could aid the Swedish troops. The harsh climate took its toll as well, as Charles marched his troops through Ukraine.
By the time of the decisive Battle of Poltava, Charles had been wounded, one-third of his infantry was dead, and his supply train was destroyed. The king was incapacitated by a coma resulting from his injuries and was unable to lead the Swedish forces. The battle was a disaster for the king, and he fled south to the Ottoman Empire, where he set up camp at Bender with about 1000 men who were called Caroleans ("Karoliner" in Swedish). The Poltava Swedish disaster is by some historians considered the point where the Swedish Empire ended and the Russian Empire started to rise.
However, the sultan Ahmed III eventually tired of Charles' scheming and besieged the city. The Janissaries did not shoot Charles during the skirmish at Bender, but captured him and put him under house-arrest in Constantinople. During his imprisonment the King played chess and studied the Turkish navy.
Meanwhile, Russia and Poland regained and expanded their territories. Great Britain, an ally of Sweden, defected from its alliance obligations while Prussia attacked Swedish holdings in Germany. Russia seized Finland and Augustus II regained the Polish throne.
Charles succeeded in leaving his imprisonment in Constantinople and returned to Swedish Pomerania on horseback, riding across Europe in just fifteen days. His efforts to reestablish the Swedish empire failed. He had two Turkish style war-ships built in Sweden, the Yildirim ("The Lightning") and the Yaramaz or Jarramas ("The Rogue"). He invaded Norway in 1716, occupied the capital Christiania, today Oslo, and laid siege to the Akershus fortress. However, the siege was lifted after the defeat of the Swedish supply fleet by Tordenskjold at the battle of Dynekilen.
In 1718 Charles once more invaded Norway and laid siege to the strong fortress of Fredriksten, overlooking the border town of Halden. While inspecting trenches close to the perimeter of the fortress, he was mortally hit by a projectile on December 11 (November 30 Old Style), 1718. The successful invasion was abandoned, and Charles' body was brought across the border. Another army corps under Carl Gustaf Armfeldt marched against Trondheim, but had to make a retreat, during which most of the 5,000 soldiers perished in a severe winter storm.
The exact circumstances around Charles' death are unclear. The most likely theory is that he was hit by a bullet from a Norwegian musket, but he may also have been killed by a grapeshot bullet from a cannon. Another theory is that he was killed by one of his own uniform buttons that had been re-made into a bullet. The button-bullet theory is coupled with speculation that he was shot from the Swedish side, making his death an assassination, because he should allegedly have been unpopular in Sweden at the time.
The most recent and thorough study was presented in 2005 by Peter From. With the help of expertise from around the world, From argues that the mortal bullet was fired by a Norwegian musket. The theory has gained support by renowned historians Peter Englund and Dick Harrison, among others.
Charles was succeeded to the Swedish throne by his sister, Ulrika Eleonora. As Palatinate-Zweibrücken required a male heir, Charles was succeeded as ruler there by his cousin Gustav Leopold. Von Görtz, Charles' minister, was beheaded in 1719.
Ragnhild Hatton, Charles XII. London, 1968.