The Role of Sweden in the Thirty Years’ War

The brief, brilliant campaigns of Gustavus Adolphus dominate the history of the Thirty Years’ War for many.  More broadly, the duel between Swedish and Imperial forces has become the defining conflict of the war, with the twelve years that preceded it being relegated to the background.  Sweden was motivated more by political concerns than by religion, but for many, it became the champion of the Protestant cause, and Gustavus Adolphus became a martyr.

Between 1618 and 1630, Imperial forces performed well in the war.  The original rebellious provinces in the Habsburg Crown lands were recovered, the Elector Frederick V was driven from the Palatinate, and Denmark had been defeated thoroughly.  Sensing final victory, the Emperor Ferdinand proclaimed the Edict of Restitution, restoring to the Catholic Church all lands that had previously been seized by Protestant princes.

This decision alienated many Protestants who otherwise might have remained loyal.  There were two main forms of Protestantism in Central Europe at the time, Lutheranism and Calvinism, and these two strains were possibly more antagonistic to each other than they were to Catholicism.  Many Lutherans had stayed out of the first twelve years of the war, only to be pushed to rebellion by 1630.

Moreover, almost as an afterthought, the Emperor gave aid to the King of Poland in his war against Sweden.  Success against Denmark had freed up large numbers of troops, and King Sigismund of Poland was a relative by marriage of Emperor.  In Imperial eyes, it was a natural enough form of assistance; to Sweden, it amounted to intervention.  Seen alongside Imperial successes against Denmark, placing Imperial power along the Baltic Sea, it seemed to the King of Sweden that the Emperor was systematically encroaching upon his sphere of influence.

The decision of Gustavus Adolphus to intervene in the German conflict was undertaken primarily to address these issues.  By reversing the Emperor’s successes, Gustavus Adolphus meant to push him away from the Baltic.  At the same time, such an adventure was only possible because of other considerations, namely the search by German Protestants for a champion in the face of the Edict of Restitution, and the desire by France to check the power of Spain and the Empire.

The chief Swedish asset was a well-trained and experienced army organized on new lines.  Traditional armies, such as those fielded by the Emperor’s generals, were built on large bodies of troops arranged in blocks that were difficult to maneuver.  A new system, pioneered among the Dutch, called for smaller battalions that were more easily maneuvered.  Based in large measure on Roman tactics, this Nassau system was adopted by the Swedes and used to good effect.

With money made available by France and the prospect of support from German Protestants, Gustavus Adolphus moved quickly, landing his army at Peenemünde in July, 1630.  Although most of the surrounding territory was potentially friendly, from a religious perspective, there were still Imperial forces to be defeated, and Swedish gains were slow for the rest of 1630.

Imperial response was also slow, largely due to conflict in Italy concerning the succession in Mantua and political challenges to the Emperor among the Electors.  The recognition of trouble in Mecklenburg came only gradually.

In the first months of 1631, Count Tilly gathered his forces to face the Swedes.  Gustavus Adolphus was also looking for his opportunity to smash Tilly’s forces, but he moved slowly as well, permitting Tilly to strike at the Protestant center of Magdeburg.  Gustavus Adolphus countered with an attack on Frankfurt an der Oder, but still Magdeburg fell.

Gustavus Adolphus was in danger of alienating himself from the Protestants of northern Germany, but during the summer, Tilly issued an ultimatum to Saxony, and when Saxony refused to disband its own forces, Tilly attacked.  This spurred Saxony on to making an alliance with Gustavus Adolphus, and with Saxon forces added, the Swedish king had some 42,000 men under his command.  With this force, he decisively defeated Tilly at Breitenfeld, on September 17.

While Tilly retreated, the Protestant forces divided up again, with the Swedes marching southeast into Bavaria while the Saxons marched southwest into Bohemia.  Under the logic of seventeenth-century warfare, it made no sense to press on against Tilly and seek the total destruction of his army; logistical concerns required the victorious armies to seek new quarters from which they could better sustain themselves.

It was not until March of 1632 that Gustavus Adolphus struck again at Tilly.  Setting out from Nuremberg, he sought to take all of Bavaria and then strike into Habsburg territory.  Tilly and the Duke of Bavaria tried to muster a defense at the river Lech, but on April 5 the Swedes defeated them, killing Tilly.  After ravaging much of Bavaria, the Swedes then marched west towards Swabia.  Bad news from the east turned him around.

The almost total reversal of fortune forced the Emperor to restore the position of Wallenstein, who raised a large army and succeeded in driving back the Saxons.  Without Swedish intervention, he would have been able to threaten Saxony and Mecklenburg.  Therefore, Gustavus Adolphus pressed with all speed for an encounter with Wallenstein.

On November 14, Wallenstein gave the order for his men to separate into winter quarters, expecting a renewal of hostilities in the spring.  His headquarters were located in the town of Lützen.  Two days later, Gustavus Adolphus attacked.  Wallenstein’s effective force numbered only around 19,000, which left the two sides evenly matched.  Over the course of six hours, Wallenstein’s forces were decisively beaten.

It was a pyrrhic victory for the Swedes, however.  Firstly, Gustavus Adolphus himself was killed in the fighting, brought down with three bullet wounds.  Secondly, the losses that the Swedes sustained were irreplaceable, destroying most of the inner core of trained professionals from Sweden.  Most of the remaining troops were mercenaries, and with the enemy now emulating the Nassau system as well, Swedish forces would henceforth enjoy no particular advantages.

The Swedes did not engage in any new major offensives until 1634, in which they renewed the old plan in which the Saxons struck into Bohemia while the Swedes, with some additional allies, marched on Bavaria.  Again the plan met with early successes followed by reversal.  The Saxons were driven back from Prague, and Imperial forces recaptured key Bavarian cities, especially Regensburg and Donauwörth.

Now the Imperial forces awaited reinforcements from Spain, and with this in mind, they laid siege to Nördlingen.  The Spanish arrived a few days before the Swedes, giving the Imperial side more time to dig in.  The Swedish army arrived with some 25,000 men, facing a larger enemy, and from the 5th to the 6th of September the battle raged; the Swedes were decisively defeated, and forced to give up a large swath of ground in their escape.

Sweden remained in the fight for the duration, but henceforth it was only one faction among many, which now included the French, who entered the fight against the Emperor on their own instead of through proxies.  It was the French victory at Rocroi in 1643 that broke the stalemate that set in after Nördlingen.  In 1643 and 1644, the Swedes redirected some of their energies against Denmark, resolving some prior disputes, but in 1645 they won a victory at Jankov in southern Bohemia.  This victory paved the way for the Peace of Westphalia, signed in 1648.

Sweden had entered the war when it seemed all but won by the Emperor.  For a brief period of time, the Swedes had seemed almost invincible, bringing new life to the Protestant side.  When Gustavus Adolphus was killed, Sweden became just another faction in a complex network of interested parties, but throughout the remainder of the war, it was an important faction.  In the end, it played a significant role in creating the terms for the peace treaty.  For subsequent generations, Sweden provided the only larger-than-life figure in its fallen king, Gustavus Adolphus.


Childs, John.  Warfare in the Seventeenth Century.  Cassell & Co., 2001.

Cowley, Robert and Geoffrey Parker, eds.  The Reader’s Companion to Military History.  Houghton Mifflin, 1996.

Parker, Geoffrey, ed.  The Thirty Years’ War (Second Edition).  Routledge, 1997.


© 2011, 2013.  All rights reserved.