In 1637 Scotland exploded in rebellion against King Charles I. The rebellion sought not only to undo hated anglicising policies in the Church, but to reverse the wholesale transfer of power to London which had followed the 1603 Union of the Crowns. The Covenanters fought for a Scottish parliament free from royal control as well as for a Presbyterian Church. Their success was staggering. When the king refused to make concessions they widened their demands, and when he planned to conquer Scotland with armies from England and Ireland, they occupied the north of England with their own army and even forced the humiliated king to pay for it. The Covenanters had triumphed, but the triumph proved fragile, as their success destabilised Charles I's other two kingdoms. The Scots had proved how brittle the seemingly absolute monarchy really was. First the Irish followed the Scottish army and revolted, then in 1642 England collapsed into civil war. How were the Covenanters to react? In the three-kingdom monarchy, Scotland's fate would depend on the outcomes of the Irish and English wars.
It was decided that Scotland's national interests - and doing God's will - made it necessary to send armies to intervene in both Ireland and England to enforce a settlement on all three kingdoms that would protect Scotland's separate identity and impose Scottish Presbyterianism on all of them. As the Covenanters launched an invasion of England in 1644 their hopes were high. Political realism and religious fanaticism were leading them to launch a bold bid to replace English dominance of Britain with Scottish.