Overview

The Swedish intervention in the Thirty Years’ War, which took place between 1630 and 1635, was a major turning point of the war, often considered to be an independent conflict. After several attempts by the Holy Roman Empire to prevent the spread of Protestantism in Europe, King Gustav II Adolf of Sweden ordered a full-scale invasion of the Catholic states. Although he was killed in action, his armies successfully defeated their enemies and gave birth to the Swedish Empire after proving their ability in combat. The new European power would last for a hundred years before being overwhelmed by numerous enemies in the Great Northern War.

Background

The king of Sweden, Gustav II Adolph, had been well informed of the war between the Catholics and Protestants in the Holy Roman Empire for some time, but his hands were tied because of the constant enmity of Poland. The Polish royal family, the primary branch of the House of Vasa, had once claimed the throne of Sweden.

Lutheranism was the primary religion of Sweden, and had by then established a firm grip on the country, but it was not solely the result of religious sentiment that Sweden converted. Notably, one of the reasons that Sweden had so readily embraced it was because converting to Lutheranism allowed the crown to seize all the lands in Sweden that were possessed by the Roman Catholic Church. As a result of this seizure and the money that the crown gained, the crown was greatly empowered.

Gustav was concerned about the growing power of the Holy Roman Empire, and like Christian IV before him, was heavily subsidized by Cardinal Richelieu, the chief minister of Louis XIII of France, and by the Dutch.

Sweden’s Army

During this time, and while Sweden was under a truce with Poland, Gustav established a military system that was to become the envy of Europe. He drew up a new military code. The new improvements to Sweden’s military order even pervaded the state by fueling fundamental changes in the economy. The military reforms—among which tight discipline was one of the prevailing principles—brought the Swedish military to the highest levels of military readiness and were to become the standard that European states would strive for.

The severity of discipline was not the only change that took place in the army. Soldiers were to be rewarded for meritorious service. Soldiers who had displayed courage and distinguished themselves in the line of duty were paid generously, in addition to being given pensions. The corp of engineers were the most modern of their age, and in the campaigns in Germany the population repeatedly expressed surprise at the extensive nature of the entrenchment and the elaborate nature of the equipment.

Swedish Intervention

From 1630 to 1634, Swedish-led armies drove the Catholic forces back, regaining much of the lost Protestant territory. During the campaign, Sweden managed to conquer half of the imperial kingdoms, making it the continental leader of Protestantism until the Swedish Empire ended in 1721.

Swedish forces entered the Holy Roman Empire via the Duchy of Pomerania, which had served as the Swedish bridgehead since the Treaty of Stettin (1630). After dismissing Wallenstein in 1630, from fear he was planning a revolt, Ferdinand II became dependent on the Catholic League. Gustavus Adolphus allied with France and Bavaria.

At the Battle of Breitenfeld (1631), Gustavus Adolphus’s forces defeated the Catholic League led by Tilly. A year later, they met again in another Protestant victory, this time accompanied by the death of Tilly. The upper hand had now switched from the Catholic League to the Protestant Union, led by Sweden.

King Gustav of Sweden

The victory of Gustavus Adolphus at the Battle of Breitenfeld (1631).

A painting of Gustav of Sweden riding a horse on a hill overlooking a battlefield and countryside.

With Tilly dead, Ferdinand II returned to the aid of Wallenstein and his large army. Wallenstein marched to the south, threatening Gustavus Adolphus’s supply chain. Gustavus Adolphus knew that Wallenstein was waiting for the attack and was prepared, but found no other option. Wallenstein and Gustavus Adolphus clashed in the Battle of Lützen (1632), where the Swedes prevailed, but Gustavus Adolphus was killed.

Ferdinand II’s suspicion of Wallenstein resumed in 1633, when Wallenstein attempted to arbitrate the differences between the Catholic and Protestant sides. Ferdinand II may have feared that Wallenstein would switch sides, and arranged for his arrest after removing him from command. One of Wallenstein’s soldiers, Captain Devereux, killed him when he attempted to contact the Swedes in the town hall of Eger (Cheb) on February 25, 1634. The same year, the Protestant forces, lacking Gustav’s leadership, were smashed at the First Battle of Nördlingen by the Spanish-Imperial forces commanded by Cardinal-Infante Ferdinand.

Peace of Prague

By the spring of 1635, all Swedish resistance in the south of Germany had ended. After that, the imperialist and the Protestant German sides met for negotiations, producing the Peace of Prague (1635), which entailed a delay in the enforcement of the Edict of Restitution for forty years and allowed Protestant rulers to retain secularized bishoprics held by them in 1627. This protected the Lutheran rulers of northeastern Germany, but not those of the south and west. Initially after the Peace of Prague, the Swedish armies were pushed back by the reinforced imperial army north into Germany.

The treaty also provided for the union of the army of the emperor and the armies of the German states into a single army of the Holy Roman Empire. Finally, German princes were forbidden from establishing alliances amongst themselves or with foreign powers, and amnesty was granted to any ruler who had taken up arms against the emperor after the arrival of the Swedes in 1630.

This treaty failed to satisfy France, however, because of the renewed strength it granted the Habsburgs. France then entered the conflict, beginning the final period of the Thirty Years’ War. Sweden did not take part in the Peace of Prague, and it joined with France in continuing the war.