[5] At some point in 1643, he transferred to the army of the Eastern Association, commanded by the Earl of Manchester, and in March 1644 was appointed Lieutenant colonel of a new infantry regiment raised by John Pickering.

Like Hewson, Pickering was a religious Independent with strong Anabaptist sympathies, while other officers included Major John Jubbes, a Leveller who resigned his commission in 1647, and Daniel Axtell, a Baptist and future regicide.

[13] Hewson fought at Naseby in June 1645, then took part in the offensive against Royalist strongholds in South West England, including Sherborne Castle, Lacock Abbey, Bridgwater, Bristol and Basing House.

By early 1647, its soldiers were owed more than £300,000 in wages, an enormous sum for the period, while Parliament was struggling with a shattered economy, an outbreak of the bubonic plague, and the refusal of Charles I to agree a peace settlement.

Hewson acted as one of the army's representatives in negotiations with Parliament over their arrears, and in November 1647 Sir Thomas Fairfax ordered his regiment into London to seize money for paying the troops.

[16] When the Second English Civil War began in April 1648, Hewson helped suppress the rebellion in Kent, including the storming of Maidstone, where he was commended for his bravery.

When 300 men from his regiment refused in May 1649 to serve in the proposed Cromwellian Conquest of Ireland, they were swiftly dismissed, after which Hewson helped Cromwell crush the Banbury mutiny.

[17] In late August, he arrived in Ireland as part of Cromwell's expeditionary force and was present at the Siege of Drogheda, where he allegedly set fire to a church containing nearly 100 Irish and English Royalist refugees.

[18] Shortly afterwards, Hewson replaced Michael Jones as Governor of Dublin, then participated in the relief of Arklow and the Siege of Kilkenny in March 1650, where he lost an eye.

Recalled to London for consultations in 1652, he was nominated MP for Ireland in the 1653 Barebones Parliament; unlike many of his army colleagues, he supported its dissolution, and backed Cromwell's appointment as Lord Protector, albeit allegedly with great reluctance.