In 1627 Gustavus Adolphus , the “Lion of the North”, had compared the revived Roman Catholic Church to the sea : “as one wave follows another in the sea, so the Papal deluge is approaching our shores.” Gustavus Adolphus saw himself as the protector of Protestantism in Germany and if north Germany was safe then so was Sweden. Gustavus Adolphus was an accomplished soldier and with the help of Catholic France, he freed himself from the war against Poland with the Treaty of Altmark of September 1629. By the end of 1629, Gustavus Adolphus controlled much of the east Baltic coast and effectively controlled Baltic trade.
Richelieu of France, a cardinal, wanted an alliance with the protestant Gustavus Adolphus to form a counter-weight to Habsburg power in Europe. If he could enlist the help of Maximillian of Bavaria and the Catholic League then so much the better. Both Gustavus Adolphus and Richelieu were pragmatists. Though they held opposite views on religion, they both realised that they needed each other if they were to form a realistic opposition to Ferdinand.
When Gustavus Adolphus landed on Peenemunde in Pomerania in June/July 1630 with 4,000 men, no alliance had been made. This worried Richelieu as he had no control over what Gustavus Adolphus might do. Gustavus Adolphus captured Stettin and the Neumark area in Brandenburg thus securing his communication lines with Sweden. With this done, he could push further into Germany. His task was made easier by the five year Treaty of Barwalde signed with France in January 1631. This treaty gave Sweden 1 million livres a year to fight her war while Sweden agreed to provide the men to do the fighting. Richelieu was happy with this arrangement as France did not have to do any of the fighting; Gustavus Adolphus' army was far enough away not to threaten France itself; Ferdinand's army would have to track Gustavus Adolphus' and that would mean most of the time, the emperor's army would be in Germany and away from the French border; Sweden had also promised to protect the commercial interests of France and not to interfere in Saxony and Bavaria.
One point in the Treaty of Barwalde did embarrass Richelieu. Neither side could formulate a separate peace treaty for the duration of Barwalde (1631 to 1636) and to many of Richelieu's enemies in France (and he had many) this looked as if he had tied France to an ally that was Protestant. Many of the devots in France found this hard to accept even if they did have a common enemy in Ferdinand.
Not all of Germany's northern princes welcomed Gustavus Adolphus. Both John George of Saxony and George William of Brandenburg saw his position in northern Germany as a threat to their own possessions. Both men called for a Protestant conference to be held at Leipzig. This took place between February and April 1631 where Protestant princes were persuaded to raise their own independent army. This they duly did and put it under the control of Hans George von Arnim - an able soldier who had served under Wallenstein but had left his services in disgust after the Edict of Restitution. Gustavus Adolphus had a problem. What would happen if the Protestant force allied itself to the Catholic League in defence of German liberties ? Would he have to fight two forces ?
The situation was resolved by Tilly. Before any Protestant agreement could be signed, the catholic League lead by Tilly besieged and destroyed the important city of Magdeburg. This city was also a great Protestant centre. Somehow the city - its freedom guaranteed by Gustavus Adolphus - caught fire and 20,000 civilians died. This cause much anger throughout the whole of Protestant Europe. The Dutch made an agreement with Sweden to supply the army of Gustavus Adolphus and with this assistance, Gustavus Adolphus marched on Berlin. From Berlin he completed his occupation of Pomerania. Gustavus Adolphus conquered Meckenburg where he restored the dukes whom Wallenstein had expelled and replaced with himself. His actions did much to restore Protestant confidence that had been weakened after Magdeburg.
Tilly found it very difficult to react to this as Maximillian of Bavaria had signed the secret Treaty of Fontainebleau in May 1631 with France. Maximillian promised not to aid the enemies of France while France recognised his Electoral rights. As Sweden was a recognised ally of France via Barwalde, Tilly (his master was Maximillian) could not attack Gustavus Adolphus as this would aid the enemies of France.
Tilly was in a dangerous position. His army was quartered in the Duchy of Friedland - land owned by Wallenstein. He was short of supplies and Wallenstein deliberately withheld them as he hoped that Tilly's failure could lead to his own return to power. To escape from his predicament, Tilly mistakenly attacked Saxony. There was a logical reason for him to do so - the area was well stocked with food and other provisions. His excuse for carrying out the attack was two-fold
John George had refused to enforce the Edict of Restitution which Tilly claimed was an insult to Ferdinand. He had defied the emperor by raising an army after Leipzig.
Leipzig quickly fell and John George was forced into seeking an alliance with Gustavus Adolphus (the Treaty of Coswig September 1631). Their combined forces heavily defeated Tilly at the Battle of Breitenfeld in September 1631. Gustavus Adolphus' army stood at 24,000 while John George had 18,000 soldiers in the field. Tilly had a force of 35,000 men. Tilly lost all his artillery and nearly 18,000 men. He could only retreat towards Bavaria.
With nothing to stop him, Gustavus Adolphus occupied the Lower Palatinate and the bishoprics of Mainz, Bamberg and Wurzburg. The Saxon force marched into Bohemia and captured Prague (November 1631)
Breitenfeld transformed the military and political set-up of Europe. After this battle no decent army stood in the way of Gustavus Adolphus. The speed and extent of his victories alarmed Richelieu who had always considered Gustavus Adolphus and Sweden the junior partner in the alliance. German princes in general were alarmed at the success of the Swedish king especially when he spent the winter of 1631-32 wintered in Germany and treating the area he had conquered effectively as his own. Gustavus Adolphus doled out land rewards to his successful generals and Oxenstierna was made governor-general of the region.
In December 1631, to counter the obvious power of Gustavus Adolphus, Richelieu offered French protection to any prince who asked for it. Only the Elector-Archbishop of Trier asked for it and French troops were garrisoned at Phillipsburg.
But nothing could disguise the fact that Gustavus Adolphus was the master of Germany. Maximillian rejected the claims by Richelieu that Bavaria was safe and openly sought the protection of Ferdinand. Maximillian also asked for the re-instatement of Wallenstein as he saw this as the only way to counter Gustavus Adolphus. This re-instatement duly took place in December 1631. Gustavus Adolphus used Mainz as his capital and planned for the invasion of the rest of the Holy Roman Empire. Richelieu could do nothing to stop him. After the devastating victory at Breitenfeld, Ferdinand considered withdrawing the Edict of Restitution and fleeing to Italy.
Wallenstein - ever the opportunist - saw the situation as a way to further extend his power. In April 1632, he was promised regular subsidies from Ferdinand and Spain under Phillip III; he was confirmed as Duke of Mecklenburg; he was given financial compensation for his help and he could make peace with any prince when he felt like it - but not the Duke of Saxony (this had to be vetted by an Imperial Diet). The one tie-back in this deal was that Wallenstein could not use Spanish or Catholic League troops without the proper permission.
In March 1632, Gustavus Adolphus had started his invasion of Bavaria. He defeated Tilly at the Battle of Lech in March 1632 - Tilly was fatally wounded at this battle and so the Holy Roman Empire (via Bavaria) lost one of its most experienced generals. By May 1632, Augsburg and Munich had fallen to Gustavus Adolphus. This was the peak of his power though.
After the fall of Munich, Gustavus Adolphus was less successful. He failed in his attempt to take Regensburg and in May 1632, Wallenstein had driven the Saxons out of Prague. To aid John George, Gustavus Adolphus marched north thus ending his projected drive to Vienna. He was also fearful that John George would suddenly join the forces of Wallenstein. Loyalty amongst allies then was never particularly strong,
In the summer of 1632, Gustavus Adolphus published his plans for a German settlement. His idea was to create two Protestant leagues - the Corpus Bellicum (which would be responsible for military affairs) and the Corpus Evangelicorum (which would run the civil administration). His purpose in producing these was to preserve the existing structure of states in Germany and to confirm the security of Protestants in Germany. He did not envisage himself as the head of a Protestant empire.
For Sweden he wanted to preserve the acquired territory in the south Baltic from the Vistula to the Elbe. This would satisfy Sweden's future security and the profits from port revenues and the expansion of Swedish trade would help to pay for the huge outlay Sweden had made in assisting northern Germany against the Holy Roman Emperor. Ferdinand had no interest in the plan and the plan could only succeed if Gustavus Adolphus continued to be successful at a military level.
Wallenstein had placed himself in a strategically very strong position - the Alte Fetse near Nuremburg. In September 1632, Gustavus Adolphus launched an unsuccessful attack on the Alte Feste. This failure lead to many mercenaries deserting the Swedish force. Wallenstein then marched north to Saxony and Gustavus Adolphus could do nothing about it. Wallenstein captured Leipzig - though the attack on the city was merely bait to attract Gustavus Adolphus to him.
Wallenstein planned to make his winter quarter's at Lutzen and Gustavus Adolphus attempted to make a surprise attack on the Catholic forces there. On the 16th November 1632, the Battle of Lutzen took place. There had been no surprise attack and Wallenstein had succeeded in drawing Gustavus Adolphus out into a full-scale battle. Wallenstein was defeated at this battle and he retreated into Bohemia. But Sweden had lost 15,000 men at this battle including Gustavus Adolphus.
Without their figurehead, the Protestant forces seemed to lack direction. Count Horn and Bernard of Weimar took over the Protestant forces - but their names did not have the aura of Gustavus Adolphus.
After Lutzen, many wanted a peace settlement. War had dragged on and with no obvious results for all those who had been fighting in it. Gustavus Adolphus was dead; Queen Christina of Sweden supported a peace plan; John George of Saxony wanted one. Even the original cause of the problem - Frederick of the Lower Palatinate - had died in November 1632. So why was there no settlement?
Oxenstierna still feared a resurgent Habsburg force and he used his influence to call for a meeting of Sweden, the Lower Saxon Circle and Saxony itself to discuss matters. They met in Heilbronn in March 1633 and the end result was a defensive alliance - the Heilbronn League - which existed to defend Protestantism in north Germany. John George did not join as he had reverted to supporting the Holy Roman Emperor. Catholic France and Protestant Sweden became the joint protectors of the new organisation. In November 1633, the Heilbronn League had its first victory when it invaded Bavaria and captured Regensburg - something that Gustavus Adolphus had failed to do.
Wallenstein by now had started to exceed his authority within the Holy Roman Empire. He started secret negotiations with France and Sweden which was outside of his jurisdiction. There were those in Vienna who disliked Wallenstein and when news reached the capital of the Holy Roman Empire of what Wallenstein was doing, it confirmed to them that he was unstable and unpredictable. As an example, Wallenstein had defeated the Swedish at Steinau but had released the captured generals in exchange for some fortresses in Silesia. Swedish troops were good but they needed decent commanders. Here was Wallenstein releasing their generals in exchange for castles !!
Wallenstein then ordered one of his generals to Bavaria to help Regensburg and Breisach but the general, Aldringen, was ordered not to fight the Swedish army there. This greatly angered Aldringen as the Swedes were the enemy of the Holy Roman Empire. In fact, Aldringen disobeyed his command and took on the Swedes. Disquiet about Wallenstein was not only being heard in Vienna - it was also spreading to his army.
It is difficult to account for Wallenstein actions in 1634. He was ill with gout and depression and this may have affected his decisions. He may also have been playing a very complex strategy game which no-one else understood. In early 1634, Ferdinand ordered Wallenstein's arrest. This order was made redundant when he was murdered by some of his officers in February 1634. At the time of his death, he only had 1500 men loyal to him.
The command of the Imperial army went to Ferdinand, the son of the emperor. He was married to the Spanish Infanta - thus bringing both houses of the Habsburgs even closer together. Ferdinand the son had also cultivated a friendship between himself and the brother of his wife - the Spanish Infante. He was the nominal head of the Spanish Netherlands. Both men were able military leaders and their friendship re-generated the Austrian-Spanish alliance. Both men were dedicated to turning back the tide of Protestantism in Europe.
In September 1634, both Catholic armies joined at Nordlingen. They were opposed by the Protestant army under Horn. Horn's plan was to break both armies into two separate parts and take each one on accordingly. It was a disaster. The Swedes were heavily defeated and Horn was captured. This one victory re-established Ferdinand in Europe. The Heilbronn League was in total disarray; the Protestants had no army while the Catholics had two armies in the field that had already proved themselves to be a potent force. By the Spring of 1635, all Swedish resistance in the south of Germany had ended. A peace package which had been started in 1634, ended with the Peace of Prague signed in May 1635.