Battle of White Mountain
The cause of the battle was a revolt by a group of Czech lords who threw two governors and a secretary out of the windows of Prague Castle. The incident is known as the Defenestration of Prague. The rebels quickly built up an army of 30,000 to make an independent Protestant country. The Czechs were defeated by a well-trained Imperial army after a battle lasting less than one hour. Emperor Ferdinand II replaced Frederick as King of Bohemia and then killed many who had opposed him. Others were given a choice to convert to Catholicism or to leave the country.