Charles was Count Palatine of Zweibrucken’s and Catherine, sister of Gustavus Adolphus’ eldest son and received training as a soldier before serving in the Swedish army between 1642 - 1645 in the Thirty Years War. Some years later in 1648 Christina promoted him to the army’s commander-in-chief.
He took on a challenging situation as king - Christina had put a major strain on the traditional relationship between the crown and nobility. The nobles had also stated they did not agree with Christina’s decision whilst she was queen, and now they had to work alongside the man they did not support.
In order to protect the crown from becoming bankrupt the nobility agreed to give the crown land they had gained back to the crown for a very low price. This act helped to improve their relationship with Charles. The lower estates were also satisfied as this was evidence of the nobles doing something to boost the country at their own expense. The lower estates had also been paying high taxes, so it appeared now that the nobles would need to contribute to the crown.
In 1655 Charles forced a policy of resumption - also known as the regaining of crown land. This decision was fueled by Charles taking back the crown which he felt was his right, and the lower estates gave him their total support for this. The nobles were told to give back 25 per cent of the lands they gained since November 1632 after a law was enforced through the Diet. The nobles would have faced severe consequences as a result, but the commission required to go through with this law did not achieve much since war took over the government’s time - the War of the North.
The war was begun by Charles making an attack on Poland, led by John II Casimir, but it is not known why.
Charles threw out a number of attacks on Poland, then claimed west Poland and moved on to the Vistula valley. His second attack led the Swedish army into Lithuania, then in August/September 1655 Warsaw, and Cracow in October 1655. Charles signed an alliance the following January with Frederick William who was the Great Elector of Brandenburg. John II Casimir fled after being faced with a major opposition. However, he had not disappeared but played on Sweden’s heresy and formed a Catholic alliance to defeat the ‘heretic’. John managed to succeed against the Swedish somewhat in Poland.
There came a drastic change in June 1657 after Denmark was prompted by Austria and Holland to declare war on Sweden. It was very clear why - Denmark wanted to rule the Baltic overall.
Charles brought the fight over to Denmark, attacked and was helped by an awful winter that froze the sea. He moved between islands to capture towns and cities which were not protected - Copenhagen and Zeeland were threatened. The Danish sued for peace as they were concerned over a lot of damage to their vulnerable capital. Sweden was given Skana, Halland, the Isle of Bornholm and had Swedish territories Trondheim and Bohuslan returned by the Treaty of Roskilde in 1658. This meant Sweden now had full control over the north area of the Danish Sound.
Charles was requiring more from Denmark than they wanted to give, so he lost patience with them and inflicted a full scale attack in August 1658.
Charles needed money for his last push so he requested the Diet to go to Goteborg where he was. It was there he suddenly died and his son (the future Charles XI) was four years old at the time so a regency took charge, and this finished all of Sweden’s wars. John II Casimir gave up his claim to the Swedish throne in the Treaty of Oliva 1660, and Sweden gave Poland back all the land taken since 1655.
"Charles X". HistoryLearning.com. 2015. Web.