With the rise of Lutherism in the 16th century, Austria became increasingly disunited. Many of the peasants rejected Catholicism as a feudalistic religion keeping them down, and converted to Lutherism. Ferdinand I, ruler of Austria, was an ardent Catholic and fought to keep Austria faithful to Rome. In 1526 the Czechs, under Vladistoc I invaded Austria. The Austrians, facing internal strife over the question of Protestantism and Catholicism, could not muster a sizable army to defend against the invaders. The Czechs, occupying most of the Eastern portion of the country, made a treaty with the Ferdinand I. He would deliver much of the eastern half of Austria (including Vienna) to the Czechs, and in return they would help him defeat the Lutherans. This is somewhat a puzzle to historians, as V