 Given the great number of Protestants among the ordinary population in the kingdom, and some of the nobles, the king's unpopularity soon caused the Bohemian Revolt.The Second Defenestration of Prague of 22 May 1618 is considered the first step of the Thirty Years' War.In the following events he remained a staunch backer of the Anti-Protestant Counter Reformation efforts as one of the heads of the German Catholic League.