/u/redmob5

I just started reading the Wikipedia article about the Thirty Years' War, and the "Origins of the war" section of the article alone makes Game of Thrones look like a joke.

This is a most awesome description of the 30YW! :-D

Just like many wars over non-trivial lengths of time, I think it is best understood in its constituent pieces.

Prior to the outbreak of the 30YW there were already wars over religion due to the Reformation. The Peace of Augsburg in 1555 was a compromise between Catholic and Lutheran princes, attempted to stop further spread of schism and war, brokered by Ferdinand I, regent of the emperor Charles V. This agreement is best seen as a political compromise with narrow religious agreement, for it only recognized Catholics and Lutherans. Soon, other denominations as such Calvinist gained power, yet this was not covered in the Augsburg agreement.

The agreement was thus:

1. Secular princes could determine the religion of his territory, and those who disagree may leave.

2. (Catholic) Ecclesiastical estates should remain so. If the prelate changes his religion, then that prelate forfeits his position. The implication being, the ecclesiastical states will remain Catholic for perpetuity.

3. However, within those ecclesiastical states, the knights and cities who had turned Protestant at 1525, may keep their religion. This provision was fast-tracked into a secret article and was not debated.

This agreement was soon challenged in the Cologne War, when the prince-archbishop converted to Calvinism yet refused to resign and wanted to turn his estate into a secular, hereditary, Calvinist fief. Catholic forces prevailed and Cologne remained a Catholic prince-archbishopric.

The first phase, the Bohemian revolt, happened because a weak emperor who was also King of Bohemia, wanted a conservative heir to succeed him both in the HRE and the kingdom of Bohemia. The period of weakness had allowed Protestantism to spread, and Bohemian leaders instead offered to elect the Calvinist Frederick V, elector of Palatine, as their king, if Bohemia could join the Protestant Union under protection. However, it was discovered that the Bohemians also made the same offer to other Protestant rulers, so it fragmented support among the Protestant Union. Frederick was supported by an Anglo-Dutch alliance, which dragged Spain, at war against the Dutch, into conflict. The Catholic forces defeated the Protestants and by 1623 Frederick V was in exile, remnants of his army fleeing. This led to Imperial occupation of the Palatine. This ended the first phase.

The second phase called the Danish Interlude started due to Baltic rivalry between Denmark and Sweden. Desperate for help, Frederick V of Palatine asked both Denmark and Sweden for help, two Protestant nations who until recently had been at war. Sweden proposed a limited war to restore Frederick in Palatine, but wanted to lead an alliance himself. This alarmed King Christian of Denmark, who sought to become the leader of Protestants in northern Europe. Despite rebuttal by the Danish Parliment, he personally used his own resources to send troops into Lower Saxony, in which he was also Duke of Holstein. This was the worst possible time to fight a war against the Empire, as the Empire himself had just raised a new army. Unsurprisingly, the Danish were crushed. By 1629, Christian had been defeated and Imperial forces started to roll back schismatic territories to how things were in 1555. This alarmed many Protestants.

The third phase Swedish Intervention was finally Gustavus Adolphus' turn in 1630. The well-drilled Swedish army surprised everybody and won key battles against the Imperials. But in 1632 the king himself was killed in battle, and Swedish progress gridlocked due to lack of money. Up to this point, France had funded Protestants, and the deadlock forced France to intervene directly. That led to the fourth phase Direct French Intervention.

By 1643, most belligerents had agreed to negotiate for peace in some way -- even if the meetings had to be split between two cities Osnabruck and Munster. It took until 1647-9 for all the points of peace to be agreed upon.

So, I hope that looking at the distinct phases helps explain the causes of the 30YW! I like Parker's The Thirty Years' War.