Background

After the Defenestration of Prague and the ensuing Bohemian Revolt, the Protestants warred with the Catholic League until the former were firmly defeated at the Battle of Stadtlohn in 1623. After this catastrophe, Frederick V, already in exile in The Hague, and under growing pressure from his father-in-law, James I, to end his involvement in the war, was forced to abandon any hope of launching further campaigns. The Protestant rebellion had been crushed. Frederick was forced to sign an armistice with Holy Roman Emperor Ferdinand II, thus ending the “Palatine Phase” of the Thirty Years’ War.

Dutch Intervention

Peace following the imperial victory at Stadtlohn proved short lived, with conflict resuming at the initiation of Denmark. Danish involvement, referred to as the Low Saxon War, began when Christian IV of Denmark, a Lutheran who also ruled as Duke of Holstein, a duchy within the Holy Roman Empire, helped the Lutheran rulers of neighboring Lower Saxony by leading an army against Ferdinand II’s imperial forces in 1625. Denmark had feared that the recent Catholic successes threatened its sovereignty as a Protestant nation.

Christian IV had profited greatly from his policies in northern Germany. For instance, in 1621, Hamburg had been forced to accept Danish sovereignty. Denmark’s King Christian IV had obtained for his kingdom a level of stability and wealth that was virtually unmatched elsewhere in Europe. Denmark was funded by tolls on the Oresund and also by extensive war reparations from Sweden.

Denmark’s cause was aided by France, which together with Charles I had agreed to help subsidize the war, not the least because Christian was a blood uncle to both the Stuart king and his sister Elizabeth of Bohemia through their mother, Anne of Denmark. Some 13,700 Scottish soldiers under the command of General Robert Maxwell, 1st Earl of Nithsdale, were sent as allies to help Christian IV. Moreover, some 6,000 English troops under Charles Morgan also eventually arrived to bolster the defense of Denmark, though it took longer for them to arrive than Christian had hoped, due partially to the ongoing British campaigns against France and Spain. Thus, Christian, as war-leader of the Lower Saxon Circle, entered the war with an army of only 20,000 mercenaries, some of his allies from England and Scotland, and a national army 15,000 strong, leading them as Duke of Holstein rather than as King of Denmark.

War Ensues

To fight Christian, Ferdinand II employed the military help of Albrecht von Wallenstein, a Bohemian nobleman who had made himself rich from the confiscated estates of his Protestant countrymen. Wallenstein pledged his army, which numbered between 30,000 and 100,000 soldiers, to Ferdinand II in return for the right to plunder the captured territories. Christian, who knew nothing of Wallenstein’s forces when he invaded, was forced to retire before the combined forces of Wallenstein and Tilly. Christian’s mishaps continued when all of the allies he thought he had were forced aside: France was in the midst of a civil war, Sweden was at war with the Polish–Lithuanian Commonwealth, and neither Brandenburg nor Saxony was interested in changes to the tenuous peace in eastern Germany. Moreover, neither of the substantial British contingents arrived in time to prevent Wallenstein’s defeat of Mansfeld’s army at the Battle of Dessau Bridge (1626) or Tilly’s victory at the Battle of Lutter (1626). Mansfeld died some months later of illness, apparently tuberculosis, in Dalmatia.

Wallenstein’s army marched north, occupying Mecklenburg, Pomerania, and Jutland itself, but proved unable to take the Danish capital, Copenhagen, on the island of Zealand. Wallenstein lacked a fleet, and neither the Hanseatic ports nor the Poles would allow the building of an imperial fleet on the Baltic coast. He then laid siege to Stralsund, the only belligerent Baltic port with sufficient facilities to build a large fleet; it soon became clear, however, that the cost of continuing the war would far outweigh any gains from conquering the rest of Denmark. Wallenstein feared losing his northern German gains to a Danish-Swedish alliance, while Christian IV had suffered another defeat in the Battle of Wolgast (1628); both were ready to negotiate.

Negotiations and the Edict of Restitution

Negotiations concluded with the Treaty of Lübeck in 1629, which stated that Christian IV could retain control over Denmark (including the duchies of Sleswick and Holstein) if he would abandon his support for the Protestant German states. Thus, in the following two years, the Catholic powers subjugated more land. At this point, the Catholic League persuaded Ferdinand II to take back the Lutheran holdings that were, according to the Peace of Augsburg, rightfully the possession of the Catholic Church. Enumerated in the Edict of Restitution (1629), these possessions included two archbishoprics, sixteen bishoprics, and hundreds of monasteries. In the same year, Gabriel Bethlen, the Calvinist prince of Transylvania, died. Only the port of Stralsund continued to hold out against Wallenstein and the emperor, having been bolstered by Scottish “volunteers” who arrived from the Swedish army to support their countrymen already there in the service of Denmark.