On October 31, 1517, Martin Luther wrote 95 propositions challenging the sale and theology of indulgences (payments connected to church penalties). According to tradition they were posted in Wittenberg; at minimum, Luther sent them to church authorities, and they spread quickly in print. The dispute began as an academic challenge but soon became a public religious and political crisis across the empire.
In June 1520, Pope Leo X issued a papal bull (an official decree) condemning many of Luther’s teachings and giving him time to recant. This step moved the controversy from local debate toward formal discipline by the Roman church. It also raised the stakes for any German rulers or cities protecting Luther or his supporters.
On January 3, 1521, the papal bull Decet Romanum Pontificem formally excommunicated Luther. Excommunication meant Luther was officially outside the church and marked as a heretic in church law. This made conflict with imperial authorities more likely, because church decisions often shaped politics within the Holy Roman Empire.
At the Diet of Worms, an imperial assembly, Luther was questioned on April 17–18, 1521 and refused to take back his writings unless convinced by Scripture or clear reasoning. This turned a church dispute into a direct confrontation with imperial government. It also encouraged reform-minded supporters to see resistance as a matter of conscience and authority.
In May 1521, Emperor Charles V issued the Edict of Worms, outlawing Luther and banning his writings. Enforcement depended heavily on local princes and city governments, so the edict created uneven outcomes across the empire. The gap between imperial law and local practice became a defining feature of the Reformation in Germany.
In 1526, the Diet of Speyer reached a compromise that, in practice, let each territory handle the Edict of Worms for the time being. This gave reforming princes and cities room to reorganize worship and church life without immediate imperial punishment. The decision helped the movement survive and expand while the empire postponed a final settlement.
At the second Diet of Speyer, a majority tried to roll back the 1526 compromise and strengthen enforcement against reformers. On April 19, 1529, several princes and representatives of free cities issued a formal protest against that decision. The term “Protestant” came from this protest, linking the movement to both religious reform and political resistance.
From October 1–4, 1529, leading reformers met at Marburg to try to agree on key doctrines, especially the Lord’s Supper (Eucharist). Luther and Zwingli could not reconcile their differences, even though they agreed on many other points. The split made it harder to build a single, united reform movement inside the empire.
On June 25, 1530, Lutheran leaders presented the Augsburg Confession at the Diet of Augsburg as a clear statement of their beliefs. It aimed to defend reformers from charges of disorder and show continuity with historic Christianity where possible. This confession became a foundational text for Lutheran churches and clarified what was at stake politically and theologically.
In February 1531, several Protestant territories created the Schmalkaldic League, a defensive alliance meant to protect members if the empire tried to force religious uniformity. The league tied religious reform to military and diplomatic planning among German rulers. It also signaled that the conflict had become a long-term political issue, not just a debate among theologians.
In 1546, tensions erupted into open war between Emperor Charles V and the Schmalkaldic League. The fighting showed that negotiations and temporary legal compromises had not resolved the religious divide. It also demonstrated the risks for territories that had reformed their churches but still lived under imperial authority.
On April 24, 1547, imperial forces defeated the Schmalkaldic army at Mühlberg and captured key Protestant leadership. The victory strengthened Charles V’s position and made it possible for him to demand religious concessions. However, military success did not end the underlying religious conflict across the empire.
On May 19, 1547, John Frederick I of Saxony signed the Capitulation of Wittenberg after defeat, giving up the electoral title. This transferred major influence within the empire to Maurice of Saxony (from a different family branch) and weakened Wittenberg’s political position. The event showed how religious conflict could reshape the empire’s internal balance of power.
On May 15, 1548, Charles V ordered the Augsburg Interim, a temporary religious rule meant to restore many Catholic practices while making a few limited concessions (such as allowing clergy marriage in some cases). Many Protestants resisted because it appeared to undo core reforms. The backlash helped set the stage for renewed political conflict and bargaining.
On August 2, 1552, the Treaty of Passau (negotiated under Ferdinand, Charles V’s brother) suspended enforcement efforts and promised a future diet to settle religion more permanently. It also helped roll back the Augsburg Interim in practice and eased pressure on Lutheran territories. The treaty was a bridge between failed coercion and the later legal compromise at Augsburg.
On September 25, 1555, the Peace of Augsburg created the first durable legal framework for coexistence between Catholicism and Lutheranism in the Holy Roman Empire. It recognized that territorial rulers could choose between the two confessions for their lands and allowed dissenters to emigrate. The settlement ended the first phase of the Reformation-era conflict in Germany, while leaving other disputes (including future conflicts involving other Protestant groups) unresolved.
The Reformation in the Holy Roman Empire (1517–1555)