Catholic Church History
At the beginning of the dark ages, the Pope declared that the Roman church was infallible. The church quickly instituted burdensome man made rules and attempted to blot out scriptures that pointed out their error. The church raised money by teaching people that they could buy forgiveness and salvation. The Roman churches also moved the Sabbath from Saturday to Sunday in an effort to draw those who worshiped the Sun and others who detested the Jewish believers.
At first, the Pope attempted to draw everyone under his control via peaceful measures. When they were met with resistance, the following statement was made, If you will not receive brethren who bring you peace you shall receive enemies who will bring you war. If you will not unite with us in showing the Saxons the way of life, you shall receive from them the stroke of death. J.H. Merle D'Aubigne, History of the Reformation of the Sixteenth Century, b. 17, ch 2.
This ushered in a time of intense persecution, which caused many believers to flee to the mountains.