The war broke out in Swabia when a united army of several Lutheran Imperial cities occupied the Catholic town of Füssen, a possession of the Augsburg prince-bishops, and made the Imperial forces move toward the fortress of Ingolstadt in the Bavarian duchy.
However, plans to invade Austrian Tyrol in order to bar the Emperor from bringing up Italian troops did not meet the approval of the Schmalkaldic princes.
Both Duke William IV of Bavaria and the Austrian Archduke Ferdinand I of Habsburg declared themselves neutral in the conflict, allowing Charles V to concentrate a mighty Imperial army without disturbances.

Furthermore the Schmalkaldic leaders could not resolve upon delivering a battle against the entrenched Imperial troops.
On 20 July 1546 Elector John Frederick I and Landgrave Philip I were placed under the Imperial ban, under the pretext that they had deposed the Catholic Duke Henry V of Brunswick-Wolfenbüttel in 1542.
Duke Maurice of Saxony took the chance and in October with the aid of Ferdinand I of Habsburg, King of Bohemia, invaded the lands of his rival and cousin in Ernestine Saxony, forcing Elector John Frederick I to turn his troops around.
He quickly came on from Swabia and liberated Ernestine Saxony with his army, whereafter he in turn invaded Albertine Saxony and the adjacent Bohemian lands.
The onset of winter left the armed conflict inconclusive.

In Swabia the Hessian troops took no further action, while the forsaken Imperial cities, like the Lutheran princes Duke Ulrich of Württemberg and Count Palatine Frederick II chose to submit to the Emperor.
On 28 March 1547 Charles V set off for Bohemia, where he united forces with his brother King Ferdinand I of Bohemia.
Because the Bohemian Lutherans did not provide any military assistance to Elector John Frederick I, as he had hoped for, the Spanish-Imperial forces of Charles V forced him into retreat.
Due to disagreement in strategy, the League's defenses were finally routed on 24 April 1547 at the Battle of Mühlberg, where John Frederick I was taken prisoner.

After the battle, which determined the result of the war, only two cities continued to resist: Bremen and Magdeburg.
Both cities refused to pay the fines Charles imposed on them and avoided occupation by Imperial troops.
In the case of Bremen, 12,000 imperial soldiers under the command of Duke Eric II of Brunswick-Calenberg unsuccessfully laid siege from January until May. This event led to the Battle of Drakenburg on 23 May 1547, as a Protestant army of the Schmalkaldic League was plundering the nearby Principality of Calenberg.
His men and supplies exhausted, Duke Eric II and his Imperial forces went to confront the army and were quickly defeated.
During the fighting, Eric was forced to swim over the Weser river in order to save his own life.
As a consequence of the Battle of Drakenburg, the Imperial troops left northern Germany.
The war broke out in Swabia when a united army of several Lutheran Imperial cities occupied the Catholic town of Füssen, a possession of the Augsburg prince-bishops, and made the Imperial forces move toward the fortress of Ingolstadt in the Bavarian duchy. However, plans to invade Austrian Tyrol in order to bar the Emperor from bringing up Italian troops did not meet the approval of the Schmalkaldic princes. Both Duke William IV of Bavaria and the Austrian Archduke Ferdinand I of Habsburg declared themselves neutral in the conflict, allowing Charles V to concentrate a mighty Imperial army without disturbances.
Furthermore the Schmalkaldic leaders could not resolve upon delivering a battle against the entrenched Imperial troops. On 20 July 1546 Elector John Frederick I and Landgrave Philip I were placed under the Imperial ban, under the pretext that they had deposed the Catholic Duke Henry V of Brunswick-Wolfenbüttel in 1542. Duke Maurice of Saxony took the chance and in October with the aid of Ferdinand I of Habsburg, King of Bohemia, invaded the lands of his rival and cousin in Ernestine Saxony, forcing Elector John Frederick I to turn his troops around. He quickly came on from Swabia and liberated Ernestine Saxony with his army, whereafter he in turn invaded Albertine Saxony and the adjacent Bohemian lands. The onset of winter left the armed conflict inconclusive.
In Swabia the Hessian troops took no further action, while the forsaken Imperial cities, like the Lutheran princes Duke Ulrich of Württemberg and Count Palatine Frederick II chose to submit to the Emperor. On 28 March 1547 Charles V set off for Bohemia, where he united forces with his brother King Ferdinand I of Bohemia. Because the Bohemian Lutherans did not provide any military assistance to Elector John Frederick I, as he had hoped for, the Spanish-Imperial forces of Charles V forced him into retreat. Due to disagreement in strategy, the League's defenses were finally routed on 24 April 1547 at the Battle of Mühlberg, where John Frederick I was taken prisoner.
After the battle, which determined the result of the war, only two cities continued to resist: Bremen and Magdeburg. Both cities refused to pay the fines Charles imposed on them and avoided occupation by Imperial troops. In the case of Bremen, 12,000 imperial soldiers under the command of Duke Eric II of Brunswick-Calenberg unsuccessfully laid siege from January until May. This event led to the Battle of Drakenburg on 23 May 1547, as a Protestant army of the Schmalkaldic League was plundering the nearby Principality of Calenberg. His men and supplies exhausted, Duke Eric II and his Imperial forces went to confront the army and were quickly defeated. During the fighting, Eric was forced to swim over the Weser river in order to save his own life. As a consequence of the Battle of Drakenburg, the Imperial troops left northern Germany.
Schmalkaldic War