Articles related to the Bishops' Wars (1639-1640), two separate conflicts fought in 1639 and 1640 between Scotland and England, with Scottish Royalists allied to England. In 1637, Charles I, then king of both Scotland and England, imposed changes in religious practice on the Church of Scotland. These were strongly opposed by many Scots who, in 1638, signed a National Covenant and became known as Covenanters. The General Assembly of the Church of Scotland then expelled bishops from the church, turning a religious dispute into a struggle for political supremacy. The new Covenanter government raised an army to prevent Charles using force to restore his authority.