1642 – On the outbreak of the First Civil War, he enlisted for Parliament in the Earl of Essex’s lifeguard.
1644 – He transferred to the Earl of Manchester’s Eastern Association army and became a major in Colonel Fleetwood’s regiment of horse.
– Harrison fought at Marston Moor in July and was sent after the battle to report Parliament’s victory to the Committee of Both Kingdoms.
1645 – He joined the New Model Army and fought at Naseby.
– He was an enthusiastic participant in the slaughter of the Catholic defenders of Basing House, which Cromwell took by storm in October.
1646 – Harrison was elected to the Long Parliament as recruiter MP for Wendover.
– He married his cousin Catherine.
1647 – From January to May, Harrison served in Ireland at the request of Lord Lisle when he took up his appointment as Lord-Lieutenant.
1649 – Harrison commanded the military escort that brought Charles to Windsor and then to London in January.
– Harrison was nominated to the Council of State. At first, his nomination was rejected by Parliament because of his extremist views.
1650 – He was appointed President of the Commission for the Propagation of the Gospel in Wales — a body empowered to seize church livings and to fund Puritan missionaries in Wales, where the Anglican clergy had been influential in raising support for the King.
1651 – He finally took a seat on the Council in February.
1660 – Harrison was one of the first of the Regicides to be singled out for punishment. He stood by his principles and made no attempt to escape. Parliament ordered him to be arrested and imprisoned in the Tower of London in May — before Charles II had even landed at Dover.
– At his trial in October, Harrison asserted that he had acted in the name of the Parliament of England and by its authority.
– He was convicted and sentenced to be hanged, drawn and quartered on October 13th at Charing Cross. Harrison went bravely to his gruesome death, his religious zeal undiminished to the end.