In 1639, and again in 1640, Charles I, who was king of both Scotland and England in a personal union, went to war with his Scottish subjects in the Bishops' Wars. These had arisen from the Scots' refusal to accept Charles's attempts to reform the Scottish Kirk to bring it into line with English religious practices. Charles was not successful in these endeavours, and the ensuing settlement established the Covenanters' hold on Scottish government, requiring all civil office-holders, parliamentarians and clerics to sign the National Covenant, and giving the Scottish Parliament the authority to approve all of the king's councillors in Scotland. After years of rising tensions, in part caused by Charles's defeat in the Bishops' Wars and his need to fund them, the relationship between Charles and his English Parliament also broke down in armed conflict, starting the First English Civil War in 1642.