The Cologne War was a conflict between Protestant and Catholic factions that devastated the Electorate of Cologne, a historical ecclesiastical principality of the Holy Roman Empire, within present-day North Rhine-Westphalia, in Germany. The war occurred within the context of the Protestant Reformation in Germany and the subsequent Counter-Reformation, and concurrently with the Dutch Revolt and the French Wars of Religion.
Wittelsbach-Hapsburg aristocrat Ernest of Bavaria was Prince-Elector-Archbishop of the Archbishopric of Cologne and, as such, Archchancellor of the Holy Roman Empire and Duke of Westphalia, from 1583 to 1612 as successor of the expelled Archbishop Gebhard Truchsess von Waldburg.
Gebhard Truchsess von Waldburg was the archbishop-elector of Cologne from 1577 to 1588. After pursuing an ecclesiastical career, he won a close election in the cathedral chapter of Cologne over Ernst of Bavaria. After his election, he fell in love with and later married Agnes von Mansfeld-Eisleben, a Protestant canoness at the Abbey of Gerresheim. His conversion to Calvinism and announcement of religious parity in the electorate triggered the Cologne War.
The siege of Godesberg, 18 November – 17 December 1583, was the first major siege of the Cologne War (1583–1589). Seeking to wrest control of an important fortification, Bavarian and mercenary soldiers surrounded the Godesberg, and the village then of the same name, now Bad Godesberg, located at its foot. On top of the mountain sat a formidable fortress, similarly named Godesburg, built in the early 13th century during a contest over the election of two competing archbishops.