Lutheran princes and imperial cities presented the Augsburg Confession to Emperor Charles V at the Diet of Augsburg. The document was meant to explain and defend Lutheran beliefs and answer Catholic criticisms. It became a key reference point for later political alliances among Protestant territories.
At Schmalkalden, leading Protestant rulers formed the Schmalkaldic League to defend their territories if the emperor tried to enforce religious conformity. Philip I of Hesse and John Frederick I of Saxony became its main leaders. The league tied together a growing network of Lutheran princes and free imperial cities.
The Peace of Nuremberg granted members of the Schmalkaldic League temporary religious liberty and paused many legal actions over religion. This reduced immediate pressure on Protestant territories while the empire faced other threats. The pause also gave the league time to strengthen itself politically and militarily.
In early 1537, league leaders met at Schmalkalden to decide how to respond to Pope Paul III’s call for a general church council. Martin Luther had drafted the Schmalkaldic Articles (a statement of doctrine), but the league did not officially adopt them. The discussions still showed the league trying to coordinate not only armies, but also religious policy.
Charles V made peace with Francis I of France through the Peace of Crépy. With this settlement, the emperor could devote more attention and resources to internal problems in the Holy Roman Empire, including religious division. The league lost the advantage of a distracted emperor and potential outside support.
Open fighting began in 1546 between Emperor Charles V (and his allies) and the Schmalkaldic League. The conflict was both political and religious: it tested whether Protestant territories could resist imperial pressure by force. The war marked a shift from negotiation toward military decision-making in the Reformation era.
During the war, the emperor used the imperial ban (a legal act declaring someone an outlaw) against major league leaders, including John Frederick I of Saxony and Philip I of Hesse. This framed the conflict not only as a religious dispute but as punishment for rebellion. It also aimed to weaken support for the league by making its leaders legally vulnerable.
In September 1546, Schmalkaldic forces attacked Ingolstadt, a key Bavarian stronghold, but withdrew after failing to take it. The setback signaled problems with coordination and momentum for the league’s campaign on the Danube. It also helped the emperor’s side hold its defensive line in southern Germany.
Charles V’s forces defeated the Schmalkaldic army at the Battle of Mühlberg, capturing John Frederick I of Saxony. This battle broke the league’s main field army and shifted the war sharply in the emperor’s favor. After Mühlberg, the league could no longer protect its leading members through force.
After the defeat, John Frederick I was compelled to sign the Capitulation of Wittenberg, giving up the Saxon electoral dignity and major territories. The electoral title passed from the Ernestine to the Albertine branch of the House of Wettin, reshaping power politics within the empire. The agreement also symbolized the league’s political collapse after military defeat.
Philip I of Hesse, the other central leader of the league, submitted to the emperor after negotiations and was taken into custody. His imprisonment removed a key organizer of Protestant military resistance. With both top leaders neutralized, the Schmalkaldic League’s ability to act as a united alliance effectively ended.
Charles V issued the Augsburg Interim, a temporary religious settlement meant to govern the empire until a final church decision. It largely restored Catholic practices while allowing a few limited concessions (such as clerical marriage and communion in both kinds in some contexts). The decree highlighted the emperor’s attempt to reverse Protestant gains—yet its very “temporary” nature showed the conflict was not fully resolved.
Schmalkaldic League and the Schmalkaldic War (1531–1547)