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Tadhg Hogan


The Thirty Years War:  From Religious to Political Warfare


In this informative document, I will be discussing the Thirty years war. Why? I find this particular war rather interesting. It is a significant event in history and is considered by some the first modern war. It is a good example of how a religious conflict can evolve into a political one and the struggle for a balance of power in Europe.


The Cause:

In years before the Thirty Years War, there were religious tensions in the Holy Roman Empire between Catholics and Protestants. After the introduction of Protestantism in 1519 by Martin Luther, tensions were very high. There had already been a previous war on the matter which resulted in the 1555 Peace of Augsburg allowing freedom of religion concerning Catholicism and Lutheranism in the parts of the Holy Roman Empire. This was encouraged under the rule of the Holy Roman Emperor Mathias. Regardless, the thing that really kicked of the Thirty Years War was 2nd Defenestration of Prague in 1618.

The year is 1618: The future Emperor of the Holy Roman Empire and a Roman Catholic by faith, Ferdinand Habsburg II is voted King of Bohemia by the Holy Roman Parliament. The majority Protestant diet of Bohemia votes him out of office, but Ferdinand refuses to leave, instead sending his nobles to sort things out. So happens the 2nd Defenestration of Prague (which was the capital of Bohemia), in which Bohemian Protestant nobles threw Catholic nobles out of windows. This act is considered the beginning of The Thirty Years War.  Miraculously, the Catholic nobles survived falling around three-stories.  This was the first was many events during the course of Thirty Years War.


Phase one: The Bohemian Phase 1618-1625

The First Phase of Four phases in the Thirty years war was the Bohemian phase, which lasted 7 years until 1625. Bohemia had plunged itself into a civil war between Catholics and Protestants. The Protestant Bohemians were aided militarily by several Holy Roman Empire states including The Platinate and Transylvania (Transylvania in itself wasn’t actually part of the Holy Roman Empire). The Protestants were also aided financially by the Dutch. There were other notable Protestants states in the Holy Roman Empire, the most notable of which was probably Saxony, who remained neutral because they didn’t want any trouble (for now).

Spain and its territories aided their Habsburg German relatives and it’s worth noting that Spain was in a powerful state at this time and was a Habsburg Monarchy. The Bohemian Rebels were led by Heinrich Thurn who contacted Fredrick V of the Platinate who was crowned King of Bohemia. Bohemia also tried to reach out to other Protestant states such as England, Sweden and Denmark-Norway. All of which refused (for the time being) with the King of Denmark-Norway, Christian IV, stating: “Who advised to drive out Kings and seize Kingdoms?”  In 1619 Ferdinand was crowned Holy Roman Emperor and Heinrich Thurn marched on the important city of Vienna but to no avail.

In 1620 the Bohemian Revolt was successfully crushed after The Battle of the White Mountain and annexed into Habsburg Austria (another important part of the Holy Roman Empire). The Imperial Forces who won the Battle of the White Mountain were led by Johann Tserclaes or the Count of Tilly. In the aftermath of the battle, the Bohemian leadership deserted. Then, Transylvania sued for peace gaining some land of Habsburg Austria (note: Habsburg Austria was not the Holy Roman Empire but a state within it. It also held some land outside the Empire). The last major resisting force was the Platinate which was defeated and conquered in 1622. Sparse fighting continued until 1625 ending the First phase of the War.


Phase two: The Danish Phase 1625-1630

A quick note before we continue, the Thirty years war had restarted the 80 years war between Spain and The Netherlands. Therefore, Spain’s involvement was more minimal than it could have been.

Regardless, the Danish were afraid of losing their possessions within the Holy Roman Empire, being Schleswig and Holstein. So, in 1625(with French financial aid) Christian IV amassed his army and marched across the border. Christian was not successful in his invasion. The Danes lost at Dessau in 1626 to General Wallenstein and was again defeated by the previously mentioned Count of Tilly at The Battle of Lutter. The Danes were defeated yet again at Stralsund in 1628. Keep in mind that England and the Dutch were giving aid to the Danes. So, possibly weak generals and leadership led to the several Danish defeats. In 1629, Christian was forced to sign a treaty with the Habsburgs.  The Treaty of Lübeck. This resulted in Danish withdrawal, no territory changes but the Danish had stay out of the affairs of the Holy Roman Empire.


Phase Three: The Swedish Phase 1630-1635

With Catholic power rising in the Holy Roman Empire, Protestant powers began to get worried about the possible impending rise of a Catholic Empire.

The Swedes decided to intervene. 

Sweden was a Protestant power led by King Gustav II, better known as Gustavus Adolphus. They invaded after finishing a war with the Polish-Lithuanian Commonwealth. They, like the Danes, also received aid from the French, but, unlike Denmark-Norway, Sweden didn’t fail in their intervention. This is often seen as the point that the war evolved from a religious conflict into to a political one as France was Catholic and at this rate, they were only helping the Swedes in order to weaken the Hapsburgs and importantly Spain. 

Meanwhile, the Swedes landed in Protestant Pomerania, which itself was fighting the Holy Roman Emperor. There, the Swedes managed to make (or threaten) Brandenburg Prussia into giving them help. Gustavus also tried to make Saxony help but its leader, John George I, wanted Saxony to be neutral. With Wallenstein having been dismissed, Tilly invaded Saxony fearing a Saxon-Swedish Alliance, thereafter forcing John George to ask Sweden for help.

A battle was inevitable. 

In 1631, a combined Saxon-Swedish Force met Tilly at Breitenfeld.  Tilly’s much larger force was utterly defeated and both sides met again the following year at Rain, this was another Swedish victory and it saw Tilly killed.

So, why did Sweden win where Denmark lost?

Well, Sweden had a better way of recruitment. For one, the Danish relied on nobles to pay for parts of an army to fund a entire, big one. However, the Swedes used an efficient method of conscription. The Swedes were also aided by small cannons which could fire faster that regular ones.

After the events at Rain, Wallenstein was reinstated, and Swedes had to act fast. Wallenstein and Gustavus met at Lutzen, this was another Swedish victory but did see Gustavus Adolphus and his horse killed.  In 1634, Ferdinand ordered the assassination of Wallenstein, which was successfully carried out.

At this point both sides had lost most good generals, but the Swedes would lose against the Spanish at Nordlingen. The Spanish were commanded by Infante-Ferdinand. This saw Spain finally becoming involved in the wider war. In 1635, the Peace of Prague was signed which saw Sweden’s German allies and other Protestant states sue for peace. So, now it was basically Sweden vs. The Hapsburgs. Spain was also involved but they had other issues with the Dutch. This ended the Swedish phase


Phase four: The French phase: 1635-1648

Meanwhile, in France, Louis XIII and an advisor of his Cardinal Richelieu were becoming concerned that the Peace of Prague made the Hapsburgs too powerful. So, in 1635 France declared war on Spain and then the Hapsburgs the following year.

Richelieu coordinated many strategies, two of which were to fight head on and fund rebellions within Spain and the Hapsburg domains to keep their opponents busy. At first though, the French did quite poorly with the Spanish under Infante-Ferdinand driving all the way to Paris via the remaining parts of the Spanish Netherlands. Over the next four years, fighting was intense, and both sides won major and/or minor victories. But, in 1637, Ferdinand II died and was succeeded by his son, Ferdinand III.

In 1640, the war was still going nowhere, while Spain had to deal with a declared independent Portugal and as well as Catalonia, which declared itself a principality under the rule of French king Louis XIII. Portugal was financially aided by the French, so Spain had withdraw its troops from the rest of Europe to help quell the Portuguese. Meanwhile, Sweden was still fighting in the North and basically took control of the North after winning the 2nd Battle of Breitenfeld in 1642.

In the same year, Cardinal Richelieu died and so did Louis XIII the following year, leaving Louis XIV to be heir, but at this time he couldn’t really do much because he was an infant. As such, France was now under a regency led by Anne of Austria. 1644 saw an important French victory at Rocroi. This battle virtually ended the idea of Spanish invincibility, as well as showing that France was still a stable nation and would continue its rise.

After Rocroi everyone was getting sick and tired of war, so delegates began to discuss peace (though these peace talks would take a few years to come to an agreement). During the peace talks, Sweden found itself at war with Denmark-Norway, which Sweden won.

In 1646, peace talks were stepped up because everyone was getting tired of a war that had been raging for 28 years. Negotiations were held over two years in the cities of Osnabrück and Münster. In 1648, Spain and The Netherlands signed the Peace of Münster which recognised Dutch independence and ending the 80 years’ war.

Throughout 1648, Hapsburg power was weakened after the French won at Lens and the Swedes laid siege to Prague. In the same year, the Treaty of Münster was signed, which laid peace terms with France and the fighting parts of the Holy Roman Empire, but not Spain. The next treaty, the Treaty of Osnabrück, made peace between Sweden and the Holy Roman Empire. All of these peace talks are known as the Peace of Westphalia. These treaties also reinstated the terms in the Peace of Augsburg and allowed religious toleration of Calvinists.

The Peace of Augsburg is often considered to be the beginning of ‘modern’ diplomacy.



To conclude, this Twenty-Nine Year, eleven-month, three week and one day war (that’s rounded up to Thirty) was driven by different desires over the course of it. At the start, it was to protect their faith and religion. Toward the end, it was driven by geo-political desires (mostly of France and Spain).

All in all, the legacy of the Thirty Years War is complex. At the end, it saw the rise of Sweden and France, and the decline of the Holy Roman Empire as Europe’s central power as it was now really decentralised and also because of the major population loss from within the Empire.


Thank you for reading this document.


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