When news of the deal between Charles and the Confederates reached Edinburgh and London, the Scottish Covenanters and the English Parliamentarians were appalled. Once more they feared the Popish plot was upon them. Charles, allied with Irish forces, could crush Protestantism in England forever. They had to act together-and quickly.
Under pressure, the methodical and ruthless John Pym kept his cool. While the Roundhead and Cavalier forces fought it out at the First Battle of Newbury, the cancer-wracked Pym embarked on secret negotiations with the Scottish Covenanters.
His hard work came to fruition on 25th September, 1643 when the English Parliament and the Scottish Covenanters signed the Solemn League and Covenant against the Royalist- Catholic menace.
In return for a commitment to religious reform, 'according to the word of God and the example of the best reformed Churches', the Scots promised to bring an army into England to fight against the King. Once again, the religion and politics of the three kingdoms were driving the momentum of the war. Scottish, Irish and English troops were now all in conflict with each other.
Pym would die within three months - but the Covenanters kept their word and poured into England. In the North-East, they launched a wave of attacks on Charles's commander in the region, the Earl of Newcastle. Meanwhile, in the North-West, the newly imported Irish troops were helping the Royalists win a number of crucial victories. Rupert surged forward seizing Bolton, Preston, Wigan and Liverpool. With the introduction of Scottish and Welsh troops, the tenor of the conflict assumed a more brutal tone. Reprisals, executions, and massacres became increasingly common. The ferocity of the war was escalating.