The Church of Scotland grew out of the Catholic church at the Reformation in the 1560s, basing itself on Calvinist doctrine and practise to form a Presbyterian church. The following centuries saw numerous faction fights, splits and controversies over doctrine, organisation, whether or not to return to episcopacy, and control of the church by Royal and lay patrons. Struggles with Charles I and Charles II for control after the union of Scottish and English crowns in 1603 created the covenanters, following the signing of the national covenant in 1638, who were persecuted for their beliefs. The Revolution Settlement of 1690 finally established the Church of Scotland as the national church, the only Calvinist national church, but the peace did not last. The Secession Church of 1733 and the disruption of 1843 which saw a third of the church leave to form the Free Church of Scotland were only some of the divisions to split the church in later years. Many of the causes of the divisions had been addressed by the early 20th century to allow several of the main Presbyterian churches to regroup into a strong unified national church.