After Martin Luther was condemned at the Diet of Worms in 1521, he found himself in a very dangerous situation. By refusing to recant and continuing to preach what the Catholic Church considered heresy, he could very well have been executed for his actions. Indeed, the Holy Roman Emperor issued a warrant for Luther, dead or alive.
Fortunately for Luther, there were many German princes sympathetic to his cause. These local rulers had chaffed under the domineering hand of the Holy Roman Emperor and the Vatican. They felt that for too long, they had been giving up aspects of their sovereign right to rule to these larger powers. In Luther, they saw a way out.
Shortly after his excommunication, Luther found refuge under the protection of Frederick III of Saxony. Interestingly, Frederick remained publicly Catholic. It is likely that he protected Luther out of an understanding that the defrocked monk's actions would lead to better practices within the Church.
A number of other local German rulers also quickly supported Luther and offered him protection. Overall, they wanted more local autonomy, although each had his own personal motivations. For instance, Philip of Hesse wanted to use Luther's new dogma as a justification for bigamy. Albert of Prussia, on the other hand, had more political reasons to adopt Lutheranism. He was eager to sever ties with the Holy Roman Empire in order to better align Prussia with Poland, which was ruled by his uncle. He also wanted to wrest control of the territory away from the Order of the Teutonic Knights, whom he saw as a weakening force in Europe.
All this religious disruption inevitably led to violent conflict. It first began with the Peasants' War in 1524. Many German peasants thought Luther would be their champion in revolting against what they considered to be an overbearing nobility. Other reformers, such as Storch and Muntzer, had preached liberal ideas and encouraged rebellion to the peasantry for years. Many of the lower classes thought that Luther would support them as well. His liberal preachings seemed to suggest as much. However, when they finally did revolt, Luther remained loyal to the nobles. He still needed the leaders' support for his own protection and to allow his nascent church to grow. As a result, many peasants were slaughtered.
Violence continued with the numerous religious wars that followed. Some violence started as peasants used Reformation teachings to advocate for social reform. These were brutally squashed by the ruling powers. Others occurred when Catholic powers, such as the Holy Roman Empire, tried to regain lands lost to them. Many Protestant principalities banded together to resist this. This violence continued for decades until the Peace of Augsburg in 1555, which officially allowed each prince within the Holy Roman Empire to decide which denomination his people would follow.