After the inauguration of the Protestant Union in 1608, Duke Maximilian of Bavaria began negotiations for the formation of this league. An alliance was finally concluded in 1609 at Munich by Augsburg, Constance, Passau, Ratisbon, and Würzburg. The confederates promised to defend the Catholic religion within the Empire, and prevent encroachments from the Protestants. In 1611 the league won the support of Spain and the Pope, and began to gather an army, but its foundation was shaken by the formation in 1617 of a separate confederation of Bamberg, Eichstadt, Würzburg and the Provost of Ellwangen by Archduke Maximilian of Austria, a war-director of the league. However, in 1619, the league was reconstructed in two groups: the Rhenish under the Elector of Mainz, Archbishop John Cronenburg (1604-1626); and the Oberland under Bavaria. The league army totalled about 30,000 men, while that of the Protestant Union numbered only 10,000. After its first victory over the Bohemians, the history of the league, whose strength lay principally in the personality of Maximilian of Bavaria, is closely involved in that of the Thirty Years War.