¶ … War was fought mainly over religion. Lutherans and Catholics already had tension between them as the 1600s approached. Additionally, Calvinism was on the rise in Europe. Since individual leaders were sanctioning religious activities, many groups were pressed to violence. Germany and the rest of the Holy Roman Empire was fragmented politically, adding to the overall tensions in European economies and politics in the 1600s. When Matthias the King of Bohemia died without descendents his cousin Ferdinand became King of Bohemia, as well as the leader of the Holy Roman Empire. In trying to force his Catholicism on the Bohemian Hussites, Ferdinand sparked anger and violence based on religious preference and availability of choice that escalated into the Thirty Years War.
Politics greatly affected the outcomes of the Thirty Years War. Many leaders intervened based on their own religions; however, others took the opportunity to sway individual nations and make political bargains, all affecting the outcomes of the war. For example, Don Inigo Onate of Spain successfully convinced Saxony (which was Protestant) to assist against Bohemia in exchange for Lusatia, significantly changing the layout of Protestant power in Europe during the war. Concern over the security of remaining Protestant nations led to Denmark's intervention. Continual mistrust and desire for maintaining political power played a large role in the Swedish intervention and the later Swedish-French intervention. France entered the war on the Protestant side, though it was mostly Catholic, as French leaders felt threatened by the Holy Roman Empire's size and strength.
Following the Battle of Rocroi in 1643, where the French beat the Spanish, negotiations began and resulted in the 1648 Treaty of Westphalia. Most notably, the Treaty maintained that states must not interfere in the internal affairs of other states. It also established standards for binding treaties between states, setting the standard for modern international affairs. Finally, the Treaty had numerous territory adjustments to stabilize Europe in the post-war periods. It is unlikely that the Thirty Years War could have been avoided, in that considerable tensions over religion had built to such a point that peaceful resolution was unlikely. Years of war, mistrust and struggle led the states involved to understand the greater need for sovereignty, independence and non-intervention in most international affairs.
References
Asch, R.G. (1997). The thirty years war: The Holy Roman Empire and Europe, 1618-48. New York: Palgrave.
