Bohemia was to play a pivotal role in the outbreak of the Thirty Years War. Bohemia had been an area known to be religiously tolerant. The region was a mixture of Calvinists, Lutherans, Catholics and Anabaptists. They all lived in relative harmony. About two-thirds of the population was Protestant and just 10% were Catholic. Most of Bohemia's senior nobility were Catholic.
Rudolf II, as the Catholic Holy Roman Emperor, wanted to remove the Protestants from the region but this was an impossible task. Bohemia was one of the more important economic regions of the empire and it was a melting pot of all religions whose people brought their respective expertise to the area.
Rudolf could not concentrate on Bohemia as he felt threatened by his brother Matthias and he needed the support of the Bohemian Estates if he was to maintain his strength within the empire. Bohemia could, if necessary, provide him with money and men in any clash with Matthias.
In July 1609, Rudolf granted the Letter of Majesty which guaranteed freedom of conscience for all; the liberty of worship for nobles and those towns belonging to the crown and the control of ecclesiastical organisation within Bohemia was to rest with the Bohemian Estates. This agreement gave Bohemia the right to effectively control their religious structure free from imperial interference. However, Rudolf did not see this agreement as being permanent.
In 1611, Rudolf attempted to assert his authority over Bohemia The Bohemian Estates called on Matthias to help them and Rudolf's attempt came to nothing but it had marked out to the nobles in Bohemia the way events might turn in the future. In return for his support, Matthias was crowned King of Bohemia and from 1611 to 1616, there was relative peace in the region.
In 1612, Rudolf died and Matthias became Holy Roman Emperor. He remained childless and the obvious question that needed to be answered was who would succeed him ? The Habsburgs wanted Archduke Ferdinand of Styria. He was a hard line Catholic who would not tolerate non-Catholics in Bohemia. The Catholic nobles of Bohemia elected Ferdinand King of Bohemia in June 1617. The Protestants of Bohemia had reason to fear this appointment as they had wanted the Elector of Saxony or the Elector Palatine. Ferdinand was offered the title on condition that he upheld the Letter of Majesty. Ferdinand agreed to do this but did not feel obligated to be bound by the letter.
Ferdinand's approach to running Bohemia was seen in his appointment of the ten deputies he needed to help him run Bohemia. Seven were Catholic and only three were Protestant despite the Catholics only forming 10% of the area's population.
The region's Protestants fell out with Ferdinand over what appeared to be a trivial incident concerning two churches at Klostergrab and Brunau. This lead to two Catholic Deputies (Martinitz and Slavata) being thrown out of a window at a Prague government office - a traditional Bohemian way of showing your anger against someone in authority. This incident is known as the “Defenestration of Prague” and it was a deliberate challenge to the authority of Ferdinand.
In a direct challenge to Ferdinand, the Bohemian Protestants appointed 36 Directors to administer Bohemia. The Estates agreed to this. A national militia was set up under Count Thurn as the Estates believed that Ferdinand was sure to make a stand. The militia had no money, no military experience and only the most basic of equipment. Also support for the militia was minimal as the peasants believed that the Estates were simply trying to advance their own position in Bohemia but that they, the peasants, would have to fight if it came down to this. If the Bohemian Estates wanted to be successful, they needed foreign support as they were not likely to get it from the people of Bohemia who thought that they had nothing to gain from the venture.
Foreign support was difficult to get. The Dutch promised some help but were extremely vague as to what that help would be; Charles Emmanuel of Savoy sent 2,000 men and Ernst von Mansfeld to command them. The Evangelical Union was on the verge of breaking up so the Protestant North German states were in no position to help.
In March 1619, Matthias died and Ferdinand became Holy Roman Emperor and King of Bohemia. Ferdinand made it his crusade to re-Catholicise the empire. Other eastern states in the Holy Roman Empire feared this approach and Lusatia, Moravia and Silesia agreed to support Bohemia. They believed that if they stood alone, they would be easily picked off by Ferdinand. But as a union of four, they stood a better chance. Even the Habsburg's Upper Austria was opposed to what Ferdinand was doing.
In July 1619, the Act of Confederation was signed between Bohemia, Lusatia, Moravia and Silesia. This agreement stated that the crown of Bohemia would remain elective; Austria and Hungary would be incorporated into the Confederation if circumstances were right; the Letter of Majesty would be upheld and that crown land and confiscated Catholic property would pay for the Confederation.
The Confederation had to appoint a new king. The rebels chose Frederick, Elector of the Palatine. Frederick's father-in-law was James I of England and Scotland. It was hoped that this connection would give the Confederation more authority and clout. But James would have none of it - least of all did he want to get involved in an eastern European problem.
In August 1619, the Bohemian throne was declared vacant by the Estates and it was duly offered to Frederick. He arrived in Prague in October 1619 having accepted the crown. War clouds were gathering fast.
The Habsburg's, from both Spain and Austria, could not allow Bohemia to rebel if only that the example set by a successful rebellion could spell doom for the Holy Roman Empire. If Bohemia was successful, other states could also be.
Spain improved her relations with Sigismund of Poland and sent a fleet to Flanders. Phillip III made plans to occupy the Lower Palatinate as in Phillip's reckoning “these measures are so urgent… Germany simply cannot be lost.”
In 1620, the Spanish general Spinola, moved his forces from Flanders to the Palatinate and took over Frederick's most prized territory - the Lower Palatinate on the left bank of the River Rhine.
Maximillian of Bavaria offered Ferdinand the armed forces of the Catholic League. Secretly, Ferdinand had offered the Electoral title held by Frederick to Maximillian so his motives were not entirely altruistic.
Ferdinand accepted Maximillian's offer and in July 1620, 30,000 troops under Count von Tilly moved into Austria and the Austrian Estates were forced to break their alliance with Bohemia. From Austria, Tilly marched into Bohemia.
Frederick's army faced Tilly alone. His army was lead by Christian of Anhalt and Thurn. Appeals for foreign help had not been successful. The Dutch offered 5,000 troops and 50,000 florins per month (about £5000). James I stayed outside of the problem. Most of Germany signed the Treaty of Ulm in 1620 in which they declared their neutrality.
On November 8th, 1620, Frederick's army was destroyed at the Battle of White Mountain, west of Prague. Frederick was forced into exile. The territory of the rebels was confiscated and a Regional Commission was created by Ferdinand to establish the Holy Roman Emperor's rights over these territories.
In June 1621, 27 rebel leaders were executed. By December 1621, 486 estates had been confiscated. All Protestant ministers were forced to leave Bohemia by 1624 and in 1627, all Bohemian families had to make a choice : Catholic or exile. Over 30,000 families emigrated. By 1650, the population of Bohemia had fallen by 50%. Those that remained found their obligations to their masters increased which provoked a short-lived revolt in 1624.
In May 1627, Bohemia was made a hereditary possession of the Habsburgs. All rights of towns and nobles were abolished. German became the official language of Bohemia and only Catholicism was tolerated.
The revolt in Bohemia had been disastrous for the Bohemians but it had also left an important strategic area of Europe in the hands of the Catholics. Protestant leaders of Europe were not willing to tolerate this.