Charles, like all kings, was styled by a royal title, which combined all his titles into one single phrase. This was:
We Charles, by the Grace of God King of Sweden, the Goths and the Vends, Grand Prince of Finland, Duke of Scania, Estonia, Livonia and Karelia, Lord of Ingria, Duke of Bremen, Verden and Pomerania, Prince of Rugen and Lord of Wismar, and also Count Palatine by the Rhine, Duke in Bavaria, Count of Zweibrucken–Kleeburg, as well as Duke of Julich, Cleve and Berg, Count of Veldenz, Spanheim and Ravensberg and Lord of Ravenstein.
The fact that Charles was crowned as Charles XII does not mean that he was the 12th king of Sweden by that name. Swedish kings Erik XIV (1560–1568) and Charles IX (1604–1611) gave themselves numerals after studying a mythological history of Sweden. He was actually the 6th King Charles. The non-mathematic numbering tradition continues with the current King of Sweden, Carl XVI Gustaf, being counted as the equivalent of Charles XVI.
Around 1700, the monarchs of Denmark–Norway, Saxony (ruled by elector August II of Poland, who was also the king of Poland-Lithuania) and Russia united in an alliance against Sweden, largely through the efforts of Johann Reinhold Patkul, a Livonian nobleman who turned traitor when the "great reduction" of Charles XI in 1680 stripped much of the nobility of lands and properties. In late 1699 Charles sent a minor detachment to reinforce his brother-in-law Duke Frederick IV of Holstein-Gottorp, who was attacked by Danish forces the following year. A Saxon army simultaneously invaded Swedish Livonia and in February 1700 invested Riga, the most populous city of the Swedish Empire. Russia also declared war (August 1700), but stopped short of an attack on Swedish Ingria until September 1700.
Charles's first campaign was against Denmark–Norway, ruled by his cousin Frederick IV of Denmark, For this campaign Charles secured the support of England and the Netherlands, both maritime powers concerned with 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 forced Denmark–Norway to make peace within months, King Charles turned his attention upon the two other powerful neighbors, King August II (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, ironically on the same day that Denmark came to terms.
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 (November 1700). The Russians outnumbered the Swedish army of ten thousand men by almost four to one. Charles attacked under cover of a blizzard, effectively split the Russian army in two and won the battle. Many of Peter's troops who fled the battlefield drowned in the Narva River. The total number of Russian fatalities reached about 10,000 at the end of the battle, while the Swedish forces lost 667 men.
Charles did not pursue the Russian army. Instead, he 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 Augustus as king of the Polish–Lithuanian Commonwealth, Charles XII put Stanislaw Leszczynski as his puppet on the Polish throne (1704).
While Charles won several decisive battles in the Commonwealth and ultimately secured the coronation of his ally Stanislaw Leszczynski and the surrender of Saxony, the Russian Tsar Peter the Great embarked on a military reform plan that improved the Russian army, using the effectively organized Swedes and other European standards for role model. Russian forces managed to penetrate Ingria and established a new city, Saint Petersburg, there. Charles planned an invasion of the Russian heartland, allying himself with Ivan Mazepa, Hetman of the Ukrainian Cossacks. The size of the invading Swedish army was peeled off as Charles left Leszczynski with some 24,000 German and Polish troops, departing eastwards from Saxony in late 1707 with some 35,000 men, adding a further 12,500 under Adam Ludwig Lewenhaupt marching from Livonia. Charles left the homeland with a defense of approximately 28,800 men, with a further 14,000 in Swedish Finland as well as further garrisons in the Baltic and German provinces.
After securing his "favorite" victory in the Battle of Holowczyn, despite being outnumbered over three to one against the new Russian army, Charles opted to march eastwards on Moscow rather than try to seize Saint Petersburg, founded from the Swedish town of Nyenskans five years earlier. Peter the Great managed, however, to ambush Lewenhaupt's army at Lesnaya before Charles could combine his forces, thus losing valuable supplies, artillery and half of Lewenhaupt's men. Charles' Polish ally, Stanislaw Leszczynski, was facing internal problems of his own. Charles expected the support of a massive Cossack rebellion led by Mazepa in Ukraine, with estimates suggesting Mazepa of being able to muster some 40,000 troops, but the Russians subjugated the rebellion and destroyed its capital Baturin before the arrival of the Swedish troops. The harsh climate took its toll as well, as Charles marched his troops for winter camp in 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. With the numbers of Charles' army reduced to some 23,000, with several wounded and handling the siege of Poltava, his general Carl Gustav Rehnskiold had a clearly inferior force to face the fortified and modernized army of Tsar Peter, with some 45,000 men. The Swedish assault ended in disaster, and the king fled with a small entourage south to the Ottoman Empire, where he set up camp at Bender with some 1,000 of his Caroleans ("Karoliner" in Swedish). The Swedish defeat at Poltava is considered by some historians to be the point where the downfall of the Swedish Empire was consummated and the Russian Empire was founded. The remainder of the army surrendered days later at Perevolochna under Lewenhaupt's command, most of them (including Lewenhaupt himself) spending the rest of their days in Russian captivity.
The Turks initially welcomed the Swedish king, who managed to provoke a war between the Ottomans and the Russians. His expenses during his long stay in the Ottoman Empire were covered by the Ottoman state budget, as part of the fixed assets (Demirbas in Turkish), hence his nickname Demirbas Sarl (Fixed Asset Charles) in Turkey. Demirbas, the Turkish word for fixed asset, is literally ironhead (demir = iron, bas = head), which is the reason why this nickname has often been translated as Ironhead Charles. Eventually a small village named Karlstad had to be built near Bender to accommodate the ever growing Swedish population there. Sultan Ahmet III, as a gesture to the King, had bought some of the Swedish women and children put up for sale by the Russians and turned them over to the Swedes, thus further strengthening the growing community of Caroleans.
However, the sultan Ahmed III's subjects in the empire eventually got tired of Charles' scheming. His entourage also accumulated huge amounts of debts with Bender merchants. Eventually "crowds" of townspeople attacked the Swedish colony at Bender and Charles had to defend himself against the mobs and the Ottoman Janissaries involved. This uprising was called "kalabalik" (crowd) which afterwards found a place in Swedish lexicon referring to a ruckus. The Janissaries did not shoot Charles during the skirmish at Bender, but captured him and put him under house-arrest at Dimetoka (nowadays Didimoticho) and Constantinople. During his semi-imprisonment the King played chess and studied the Ottoman Navy and the naval architecture of the Ottoman galleons. His sketches and designs eventually led to the famous Swedish war ships Jarramas (Yaramaz) and Jilderim (Yildirim).
Meanwhile, Russia and Poland regained and expanded their borders. Great Britain, an adversary of Sweden, defected from its alliance obligations while Prussia attacked Swedish holdings in Germany. Russia occupied Finland (the Greater Wrath 1713 – 1721). After defeats of the Swedish army, consisting mainly of Finnish troops in the Battle of Palkane 1713 and the Battle of Storkyro 1714 ,the military, administration and clergymen escaped from Finland, which fell under Russian military regime.
Augustus II regained the Polish throne.
Charles agreed to leave Constantinople and returned to Swedish Pomerania. He made the journey on horseback, riding across Europe in just fifteen days. He traveled across the Habsburg Kingdom of Hungary to Vienna and arrived at Stralsund. A medal with Charles on horseback, his long hair flying in the wind, was struck in 1714 to commemorate the speedy ride. It reads Was sorget Ihr doch? Gott und Ich leben noch. (What worries you so? God and I live still.).
After 14 years away, Charles arrived in Sweden to find his homeland at war with Russia, Saxony, Hannover, Great Britain and Denmark. Sweden's western enemies attacked southern and western Sweden while Russian forces traveled across Finland to attack the Stockholm district. For the first time, Sweden found itself in a defensive war. Charles' plan was to attack Denmark by striking at her possessions in Norway. It was hoped that by cutting Denmark's Norwegian supply lines the Danes would be compelled to withdraw their forces from Swedish Scania.
Charles invaded Norway in 1716 with a combined force of 7,000 men. He occupied the capital of Christiania, (modern Oslo), and laid siege to the Akershus fortress there. Due to a lack of heavy siege cannons he was unable to dislodge the Norwegian forces inside. After suffering significant losses of men and material, Charles was forced to retreat from the capital on 29 April. In the following mid-May, Charles invaded again, this time striking the border town of Fredrikshald, now Halden, in an attempt to capture the fortress of Fredriksten. The attacking Swedes came under heavy cannon fire from the fortress and were forced to withdraw when the Norwegians set the town of Fredrikshald on fire. Swedish casualties in Fredrikshald were estimated at 500 men. While the siege at Fredrikshald was underway, the Swedish supply fleet was attacked and defeated by Tordenskjold in the Battle of Dynekilen.
In 1718 Charles once more invaded Norway. With a main force of 40,000 men, he again laid siege to the fortress of Fredriksten overlooking the town of Fredrikshald. Charles was shot and killed during the siege. The invasion was abandoned, and Charles' body was returned to Sweden. A second force, under Carl Gustaf Armfeldt, marched against Trondheim with 10,000 men but was forced to retreat. In the march that ensued, many of the 5,800 remaining men perished in a severe winter storm.
While inspecting trenches close to the perimeter of the fortress on 11 December (30 November Old Style), 1718, Charles was struck in the head by a projectile and killed. The shot struck the left side of his skull and exited from the right. The definitive circumstances around Charles' death are unclear however. Despite multiple investigations of the battlefield, Charles' skull and his clothes, it is not known where he was hit exactly, and whether the shot came from the ranks of the enemy or from his own men. There are several theories as to how Charles died, though none can be given with any certainty. Although there were many people around the king at the time of his death, there were no witnesses to the actual moment he was struck. The most likely theory is that Charles was killed by the Danes as he was within easy reach of the Danish guns. Even then, there are two possibilities that are usually cited: that he was killed by a musket shot, or that he was killed by grapeshot from the nearby fortress.
More sinister theories claim he was murdered: One claim is that the killer was a Swedish compatriot and asserts that enemy guns were not firing at the time Charles was struck. Suspects in this claim range from a nearby soldier tired of the siege who wanted to put an end to the war, to a murderer sent by Charles' own brother-in-law, who profited by the event, later taking the throne as Frederick I of Sweden. Another possible murderer was Fredrik's aide-de-camp, Andre Sicre, who confessed during a state of delirium brought on by fever but later recanted. It is also suspected that a plot to kill Charles may have been put in place by a group of wealthy Swedes who would benefit from the blocking of a 17% wealth tax that Charles intended to introduce.
Another odd account of Charles' death comes from Finnish writer Carl Nordling, who states that the king's surgeon, Melchior Neumann, dreamed the king had told him that he was not shot from the fortress but from "one who came creeping".
The body has been exhumed on three occasions to ascertain the cause of death; in 1746, 1859 and 1917. The 1859 exhumation found that the wound was in accordance with a shot from the Norwegian fort while the other two analyses found that he had been murdered.
Charles was succeeded to the Swedish throne by his sister, Ulrika Eleonora. As Palatinate-Zweibrucken required a male heir, Charles was succeeded as ruler there by his cousin Gustav Leopold. Georg Heinrich von Gortz, Charles' minister, was beheaded in 1719.
Exceptional for abstaining from alcohol and women, he felt most comfortable during warfare. Contemporaries report of his seemingly inhuman tolerance for pain and his utter lack of emotion. His brilliant campaigning and startling victories brought his country to the pinnacle of her prestige and power, posthumously earning him the epithet "last of the Vikings," although the Great Northern War resulted in Sweden's defeat and the end of her empire within years of his own death.
Charles' death marked the end of autocratic kingship in Sweden, and the subsequent Age of Liberty saw a shift of power from the monarch to the parliament of the estates. Historians of the late 18th and early 19th centuries viewed Charles' death as the result of an aristocratic plot, and Gustav IV Adolf, the king who refused to settle with Napoleon Bonaparte, "identified himself with Charles as a type of righteous man struggling with iniquity" (Roberts). Throughout the 19th century's romantic nationalism Charles XII was viewed as a national hero. He was idealized as a heroic, virtuous young warrior king, and his fight against Peter the Great was associated with the contemporary Swedish-Russian enmity. Examples of the romantic hero idolatry of Charles XII in several genres are Esaias Tegner's song Kung Karl, den unge hjalte (1818), Johan Peter Molin's statue in Stockholm's Kungstradgarden (unveiled on 30 November 1868, the 150th anniversary of Charles' death) and Gustaf Cederstrom's painting Karl XII:s likfard ("Funeral procession of Charles XII", 1878). The date of Charles' death was chosen by a student association in Lund for annual torch marches beginning in 1853.
In 1901, August Strindberg in his play Karl XII broke with the heroization practice, showing an introverted Charles XII in conflict with his impoverished subjects. In the so-called Strindberg feud (1910–1912), his response to the "Swedish cult of Charles XII" (Steene) was that Charles had been "Sweden's ruin, the great offender, a ruffian, the rowdies' idol, a counterfeiter." Verner von Heidenstam however, one of his opponents in the feud, in his book Karolinerna instead "emphasized the heroic steadfastness of the Swedish people in the somber years of trial during the long-drawn-out campaigns of Karl XII" (Scott).
In the 1930s, the Swedish Nazis held celebrations on the date of Charles XII's death, and shortly before the outbreak of World War II, Adolf Hitler received from Sweden a sculpture of the king at his birthday. In the late 20th century, Swedish nationalists and neo-Nazis had again used 30 November as a date for their ceremonies, however these were regularly interrupted by larger counter-demonstrations and were abandoned.
A number of Russian writers for the state coupled Charles XII with Napoleon and Hitler as foreign invaders who all came to grief when trying to invade the Russian heartland.
Apart from being a monarch, the King's interests included mathematics, and anything that would be beneficial to his warlike purposes. He is credited with having invented an octal numeral system, which he considered more suitable for war purposes because all the boxes used for materials such as gunpowder were cubic. According to a report by contemporary scientist Emanuel Swedenborg, the King had sketched a model of his thoughts on a piece of paper and handed it to him at their meeting in Lund in 1716. The paper was reportedly still in existence a hundred years later, but has since been lost. Several historians of science suspect that either the multi-talented Emanuel Swedenborg or the brilliant inventor Christopher Polhem – also present at the meeting in Lund – may have been the true inventor behind this feat, or at least a significant contributor.
Charles fascinated many in his time. Voltaire, who could be very sardonic, stopped in front of Charles and took off his hat. Samuel Johnson, a devoted anti-militarian, wrote in his poem "The Vanity of Human Wishes":
Swedish author Frans G. Bengtsson and Professor Ragnhild Hatton have written biographies of Charles XII of Sweden, as did Voltaire in 1731.
Charles XII figures quite prominently in Robert Massie's magnum opus "Peter the Great".
August Strindberg's 1901 play Carl XII
The 1925 Swedish film Charles XII was a silent epic portraying his reign. In 2007, Oleg Ryaskov again portrayed Charles XII (Eduard Flerov) in the Russian drama The Sovereign's Servant.
A character based on Charles XII plays a major role in The Age of Unreason, a series of four alternate history novels written by American science fiction and fantasy author Gregory Keyes.
A number of albums started by Ultima Thule, later including other artists, were named "Carolus Rex".
In May 2012 the Swedish heavy metal band Sabaton released an album named "Carolus Rex".
Al Stewart's song, "The Coldest Winter in Memory," deals primarily with Charles's military campaign and defeat by Peter the Great. The song is on the out-of-print 1996 album Seemed Like a Good idea at the Time and the live 2010 album Uncorked.
In his novel, Victory, Joseph Conrad compares his Swedish protagonist, Axel Heyst, to the Swedish king, "...with his bald head and long moustaches, he resembled the portraits of Charles XII, of adventurous memory."
In Roy Andersson's 2014 film A Pigeon Sat on a Branch and Reflected on Existence, a young Swedish king appears in several scenes while an army in the background sings a song about Charles XII. In one scene, the king has all the women driven out of a bar before he enters, orders water rather than beer, and takes interest in the young male bar assistant, which accords with popular depictions of Charles XII, as a bachelor and teetotaler.