CHARLES X. (CHARLES GUSTAVUS) (1622-1660), king of Sweden, son of John Casimir, count palatine of Zweibrucken, and Catherine, sister of Gustavus Adolphus, was born at Nykop ing Castle on Nov. 8, 1622. He learnt the art of war under the great Lennart Torstensson, being present at the second battle of Breitenfeld and at Jankowitz. From 1646 to 1648 he frequented the Swedish court. It was supposed that he would marry the queen regnant, Christina, and to compensate her cousin for a broken half-promise she declared him (1649) her successor, despite the opposition of the senate headed by Axel Oxenstjerna. In 1648 he was appointed generalissimo of the Swedish forces in Germany, and acted as Swedish plenipotentiary at the executive congress of Nuremberg, assembled (1650) to execute the details of the peace of Westphalia. As the recognized heir to the throne, his position on his return to Sweden was a difficult one, in view of the un popularity of the queen. Charles, therefore, wisely withdrew to the isle of Oland till the abdication of Christina (June 5, called him to the throne.
The beginning of his reign was devoted to the healing of domes tic discords and in preparation for a new policy of conquest. He contracted a political marriage (Oct. 24, 1654) with Hedwig Leonora, the daughter of Frederick III., duke of Holstein-Gottorp, by way of securing a future ally against Denmark. The two great pressing national questions, war and the restitution of the alienated crown lands, were considered at the Riksdag which assembled at Stockholm in March 1655. The war question was decided in three days by a secret committee presided over by the king, who easily persuaded the delegates that a war with Poland was neces sary and might prove very advantageous ; but the consideration of the question of the subsidies due to the crown for military purposes was postponed to the following Riksdag (see SWEDEN : History). On July 15 Charles quitted Sweden to engage in his Polish adventure. By the time war was declared he had at his dis posal 5o,000 men and 5o warships. Hostilities had already begun with the occupation of Dunaburg (Dvinsk) in Polish Livonia by the Swedes (July 1, 1655), and the Polish army encamped among the marshes of the Netze concluded a convention (July 25) whereby the palatinates of Posen and Kalisz placed themselves under the protection of the Swedish king. The Swedes then en tered Warsaw without opposition and occupied the whole of Great Poland. The Polish king, John Casimir, fled to Silesia. Mean while Charles pressed on towards Cracow, which was captured after a two months' siege. The fall of Cracow extinguished the last hope of the boldest Pole ; but before the end of the year an extraordinary reaction began in Poland itself. On Oct. 18 the Swedes invested the fortress-monastery of Czenstochowa, but the place was heroically defended ; and after a seventy days' siege the besiegers were compelled to retire with great loss.
This astounding success elicited an outburst of popular enthu siasm which gave the war a national and religious character. The tactlessness of Charles, the rapacity of his generals, the bar barity of his mercenaries, his refusal to legalize his position by summoning the Polish diet, his negotiations for the partition of the very state he affected to befriend, awoke the long slumber ing public spirit of the country. In the beginning of 1656 John Casimir returned from exile and the Polish army was reorganized and increased. By this time Charles had discovered that it was easier to defeat the Poles than to conquer Poland. His chief object, the conquest of Prussia, was still unaccomplished, and a new foe arose in the elector of Brandenburg, alarmed by the ambition of the Swedish king. Charles forced the elector, indeed, at the point of the sword to become his ally and vassal (treaty of Konigsberg, Jan. 17, 1656) ; but the Polish national rising now im peratively demanded his presence in the south. For weeks he scoured the interminable snow-covered plains of Poland in pursuit of the Polish guerillas, penetrating as far south as Jaroslav in Galicia, by which time he had lost two-thirds of his 15,00o men with no apparent result. His retreat from Jaroslav to Warsaw, with the fragments of his host, amidst three converging armies, in a marshy forest region, intersected in every direction by well guarded rivers, was one of his most brilliant achievements. But his necessities were overwhelming. On June 21 Warsaw was re taken by the Poles, and four days later Charles was obliged to purchase the assistance of Frederick William by the treaty of Marienburg. On July 18-20 the combined Swedes and Branden burgers, 18,00o strong, after a three days' battle, defeated John Casimir's army of 50,00o at Warsaw and reoccupied the Polish capital; but this brilliant feat of arms was altogether useless, and when the suspicious attitude of Frederick William compelled the Swedish king at last to open negotiations with the Poles, they refused the terms offered, the war was resumed, and Charles con cluded an offensive and defensive alliance with the elector of Brandenburg (treaty of Labiau, Nov. 2o) whereby it was agreed that Frederick William and his heirs should henceforth possess the full sovereignty of East Prussia. In the meantime the hostile Dutch dominated Danzig, and the tsar started a campaign against the Swedish Baltic provinces.
The alliance of the elector had now become indispensable on almost any terms. So serious, indeed, were the difficulties of Charles X. in Poland, in spite of the assistance of the elector and of George Rakoczy II., prince of Transylvania, that it was with extreme satisfaction that he received the tidings of the Danish declaration of war (June 1, 165 7) which enabled him honourably to emerge from the inglorious Polish imbroglio. He had learnt from Torstensson that Denmark was most vulnerable if attacked from the south, and, imitating the strategy of his master, he fell upon her with a velocity which paralyzed resistance. At the end of June 1657, at the head of 6,000 seasoned veterans, he executed a rapid march from the interior of Poland to Stettin, and reached the borders of Holstein on July 18. The Danish army at once dispersed and the duchy of Bremen was recovered by the Swedes, who in the early autumn swarmed over Jutland and firmly estab lished themselves in the duchies. But the fortress of Fredriks odde (Fredericia) on the Little Belt held Charles's little army at bay from mid-August to mid-October, while the fleet of Denmark, after a stubborn two days' battle, compelled the Swedish fleet to abandon its projected attack on the Danish islands. In July an offensive and defensive alliance was concluded between Denmark and Poland. The elector of Brandenburg joined the league against Sweden, and compelled Charles to accept the proffered mediation of Cromwell and Mazarin. The negotiations foundered, however, upon the refusal of Sweden to refer to the points in dispute to a general peace-congress, and Charles was still further encouraged by the capture of Fredriksodde (Oct. 23-24). In the middle of December 16S7 began the great frost which was to be so fatal to Denmark. On Jan. 28, 1658, Charles X. arrived at Haderslev (Hadersleben) in South Jutland, when it was estimated that in a couple of days the ice of the Little Belt would be firm enough to bear even the passage of a mail-clad host to the island of Fiinen. Early in the morning of Jan. 3o the Swedish king gave the order to start, the horsemen dismounting where the ice was weakest, and cautiously leading their horses as far apart as possible, when they swung into their saddles again, closed their ranks and made a dash for the shore. The whole of Funen was won with the loss of only two companies of cavalry, which disappeared under the ice while fighting with the Danish left wing. Charles, with his eyes fixed steadily on Copenhagen, resolved to cross the frozen Great Belt also. After some hesitation, he accepted the advice of his chief engineer officer Eric Dahlberg, who acted as pioneer throughout, and chose the more circuitous route from Svend borg, by the islands of Langeland, Laaland and Falster, in pref erence to the direct route from Nyborg to Kors˘r, which would have been across a broad, almost uninterrupted expanse of ice. On the night of Feb. 5 the transit began, the cavalry leading the way through the snow-covered ice, which quickly thawed beneath the horses' hoofs so that the infantry which followed after had to wade through half an ell of sludge, fearing every moment lest the rotting ice should break beneath their feet. At three o'clock in the afternoon, Dahlberg leading the way, the army reached Grim sted in Laaland without losing a man. On Feb. 8 Charles reached Falster. On the 11th he stood safely on the soil of Sjaelland (Zealand). The medal struck to commemorate "the glorious transit of the Baltic Sea" bore the haughty inscription: Natura hoc debuit uni.
The crushing effect of this unheard-of achievement on the Danish Government found expression in the treaties of Taastrup (Feb. 18) and Roskilde (Feb. 26, 1658), whereby Denmark sacrificed nearly half her territory to save the rest (see DENMARK : History) . But even this was not enough for the conqueror. Mili tary ambition and greed of conquest moved Charles X. to what, divested of all its pomp and circumstance, was an outrageous act of political brigandage. At a council held at Gottorp (July 7), Charles X. resolved, without any warning, in defiance of all in ternational equity, to let loose his veterans upon Denmark a sec ond time. For the details of this second struggle, with the con comitant diplomatic intervention of the western powers, who were determined to prevent the closing of the Sound, see FRED ERICK III., king of Denmark, and DENMARK : History. Only after great hesitation would Charles X. consent to reopen nego tiations with Denmark direct, at the same time proposing to exercise pressure upon the enemy by a simultaneous winter cam paign in Norway. Such an enterprise necessitated fresh subsidies from his already impoverished people, and obliged him in Decem ber 1659 to cross over to Sweden to meet the estates, whom he had summoned to Gothenburg. The lower estates murmured at the imposition of fresh burdens; and Charles had need of all his adroitness to persuade them that his demands were reasonable and necessary. At the very beginning of the Riksdag, in January 166o, it was noticed that the king was ill ; but he spared himself as little in the council-chamber as in the battle-field, till death suddenly overtook him on the night of Feb. 12-13, 166o, in his thirty-eighth year.