[5] He graduated in 1631, and in October 1634 began legal studies at Gray's Inn; prior to the outbreak of the First English Civil War in August 1642, he was employed by Parliament as diplomatic liaison with their Covenanter allies in Scotland, a role he continued into 1643.

In March 1644, he was wounded in an assault on Hillesden House led by Cromwell, and was rewarded by being made colonel of a new infantry regiment, which fought under the Earl of Manchester at Marston Moor in July, then Second Newbury in October.

[7] In April 1645, Sir Thomas Fairfax nominated Pickering as colonel of one of twelve infantry regiments in the recently formed New Model Army, although the appointment was initially opposed by the House of Lords.

The regiment fought at Naseby, then took part in the 1645 autumn offensive against Royalist strongholds in South West England, including the capture of Sherborne Castle, Lacock Abbey, Bridgwater, Bristol and Basing House.

[15] "John Pickering's Regiment of Foote" forms part of the modern Sealed Knot society, an Historical reenactment group dedicated to the English Civil War.