He entered Parliament in 1614, and by the 1620s was making his mark, especially as a manager of the impeachment of Buckingham (1626), and as a supporter of the Petition of Right (1628). In the Long Parliament his debating and tactical skills brought him great influence and earned him the nickname “King Pym”. He was the main architect of the reforming legislation of 1641, including the Acts of Attainder against Strafford and Laud, and was responsible for having the Grand Remonstrance printed and published. Pym was one of the five Members of Parliament whom Charles I tried to arrest in 1642. Once the English Civil War began, he played a role on the Committee of Safety (1642) and in 1643 engineered the Solemn League and Covenant with the Scots.