In summer 1546, armed conflict erupted in the Holy Roman Empire. The war pitted the Catholic Emperor Charles V against the Schmalkaldic League, an alliance of Protestant imperial estates led by Landgrave Philip of Hesse and Prince-Elector John Frederick of Saxony. While the conflict's most famous and final battle took place in Thuringia at Mühlberg, the Schmalkaldic War's first military action occurred in southern Germany in the Danube River basin. This area housed numerous evangelical imperial cities, several of which sat south of the Danube in eastern Swabia. When hostilities began in July 1546, magistrates throughout the region ordered their forces to occupy the local countryside. With their soldiers came the Reformation, as city councils sent preachers to reform the seized parishes. For councilors in Augsburg, Ulm, and elsewhere, evangelization complemented the general war effort, since true believers must “first and foremost consider God's word and honor … and let God's word be preached. … Such a thing should not be delayed until after the war, for if one undertakes the Christian work of improving the corrupted churches of these poor subjects now, God will grant us victory more quickly and allow the newly won Christians to remain with us.” Closely tied to the religious goals of this wartime program of reform, therefore, was the concrete political objective of spreading urban jurisdiction to areas formerly controlled by Catholic lords.