The Thirty Years' War officially broke out in 1618. However, its roots can be traced back to the Treaty of Augsburg in 1555. The then Habsburg Emperor Charles V, facing the specter of an intra-German, religious war between Roman Catholics and Lutherans, allowed Protestants certain religious freedoms. Most importantly, it allowed the local rulers of the German states to determine the religion of their subjects themselves.
However, the Protestants soon split and other doctrines sprung from their ranks, such as that of the Calvinists, for which the Treaty of Augsburg had made no provision. At the same time, the Vatican, with the support of Spain, which was fighting, as early as 1568, against the Protestant Dutch who rebelled against it, tried to impose the so-called Counter-Reformation.
Although the background of the conflict was religious, however, to describe the Thirty Years' War as a religious war would be far from the truth. Like every war, this one had political causes. The warring leaders simply exploited the religious sentiment on both sides for the benefit of their political pursuits.
The case of France is typical, which, although its official religion was Roman Catholicism, nevertheless fought on the side of the Protestants, because the only thing it was interested in was the weakening of Spain and the Habsburg Empire. Protestant Saxony was sometimes allied with the Habsburgs and sometimes aligned with the Protestant Swedes. The same was done by many German rulers and rulers of then politically fragmented Germany.
In 1593 the Holy Roman Empire, which was traditionally under the rule of the Habsburgs, became involved in the so-called "Long War" with the Ottomans. In order to face the Turks, the then emperor Rudolf II requested the financial and military assistance of all German rulers, regardless of creed. This war lasted until 1606 and left the Empire financially exhausted, while it gave the right to the Protestant rulers who participated in the emperor's favor, to hope that their services would be rewarded with more freedom, political and religious.
At that time the council of seven electors of the Empire consisted of four Roman Catholic electors (Duke of Bavaria, Archbishops of Mainz, Trier and Cologne), two Calvinists (Electors of the Palatinate and Brandenburg) and one Lutheran (Duke of Saxony). The consequence of this was to raise fears among the Habsburgs and the Roman Catholic electors that the Protestants might even seize the imperial throne.
This political concern manifested itself as a religious one, with the Duke of Bavaria Maximilian II leading the fight against the Protestant electors and especially against his neighbor, Frederick of the Palatinate, whose territories he claimed. Frederick of the Palatinate was considered the strongest elector of the Empire and he made sure to further strengthen his position by appearing as the champion and protector of the Protestants of the Empire, placing himself at the head of the Protestant or Evangelical Union, a political entity to which all the Protestant German rulers joined.
Against him Frederick had not so much the Habsburg emperor, who, due to the Long War with the Turks, but also the new conflicts with them (1615-17), could not afford to face him, but the competitor of Maximilian II ' of Bavaria, who, for his part, emerged as a champion of the Counter-Reformation and a defender of Roman Catholicism in Germany, thus serving his political ambitions. Maximilian founded the Catholic League, as a counterweight to the Protestant Union, and began to gather troops, just as his opponent was doing. Already the seed of war had been planted.
Bohemian revolution
After the death of the Habsburg emperor Rudolf B, in 1612, his brother Matthias ascended the imperial throne, who confirmed the privileges and religious freedoms of the Protestants. Matthias's aggressive policy did not satisfy the conservative Roman Catholics, such as Maximilian of Bavaria and his nephew and later successor Ferdinand.
Matthias soon lost control. He was obliged to nominate the nephew of the king of Bohemia in 1617. The new king - essentially a governor - immediately after his election, sent to Prague two Czechs, his Roman Catholic advisers, as his representatives in the assembly of the nobles of the kingdom. These two, Willem Slavata and Jaroslav Borzita, would essentially rule Bohemia on his behalf. However, the other nobles, led by Count Heinrich Matthias von Thurn, reacted. Thurn especially had personal reasons to react, as he was losing his position to Slavata as head of the Bohemian Council of Nobles.
Ferdinand's move to send the two Roman Catholic envoys was seen as offensive and a deliberate attempt to undermine the Protestant leadership of the Bohemian council of nobles. Tourne, in March 1618, summoned the Protestant nobles and representatives of the Bohemian towns to an assembly. There he said that the privileges of the Protestants that had been given to them by the Treaty of Augsburg, Ferdinand intended to abolish them.
This, of course, was a lie, as Ferdinand, when he was anointed King of Bohemia, had pledged himself to observe the "Royal Letter", the charter of Protestant privileges and rights, that is. Nevertheless, Tourne managed to convince the other nobles and representatives and win their support.
The Protestant assembly issued a relevant resolution which it sent to the emperor Matthias, requesting his intervention against his nephew and successor. Matthias again appeared condescending, replying that he would go to Bohemia himself to settle the matter, the non-existent matter in reality. At the same time, however, Matthias' moderate, otherwise prime minister, Cardinal Melchior Claesl, exasperated by Tourne's actions, sent a strongly worded letter. Turns used this letter, and not the emperor's, to absolutely convince the Protestant nobles now that they were under threat.
Speaking to the Protestant nobles, he said that they should throw Ferdinand's representatives from the windows of the Prague castle, "as is customary". The first window-dressing of Prague took place in 1419, when the then mayor of the city, together with his advisors, were thrown from the windows of Hrančany castle, where the seat of the Bohemian chancellery was also, by the rebel Usites. On May 23, 1618 Tourne and his like-minded people jumped from the window of the castle, from a height of 21m. Ferdinand's two representatives and their secretary, who survived the fall as they fell into the castle's rubbish-filled moat.
Along with the three thrown from the windows, he fell into the void and any attempt to avoid a war that could and should have been avoided. Two days after this episode the Protestant nobles formed their own diet and elected a twelve-member directorate, the members of which constituted the "Bohemian chancellery". Following these, the revolutionaries asked the emperor Matthias for the resignation of Ferdinand from the throne of Bohemia. The funny thing was that almost all the current members of the board had voted in favor of the election of Ferdinandos, just a few months before.