Reichsacht
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.