On the outbreak of the
First English Civil War in 1642, Byron and his brothers were "all passionately the King's", according to the writer
Lucy Hutchinson, a family friend. All seven Byron brothers fought on the Royalist side; the eldest, Sir
John Byron, was credited with raising the first Royalist cavalry regiment of the war, in which three of the younger brothers served as officers. Thomas Byron was appointed colonel of the
Prince of Wales' cavalry regiment, and also commanded the Prince's troop, one of seven which made up the regiment. He was knighted by
King Charles on 27 September, in
Shrewsbury. At the
Battle of Edgehill in October 1642, where the regiment fought on the Royalist's right wing, Byron saved the life of one of his men,
Richard Bulstrode, by shooting a Parliamentarian soldier who was attacking Bulstrode. In November, he was awarded a degree from
Oxford University. In the same month, during the Royalist campaign in the
Thames Valley, Byron and his older brother John occupied
Fawley Court, the home of
Bulstrode Whitelocke. The Royalist soldiers were ransacking the house, but Byron found Whitelocke's children hidden in the estate nearby, and protected them from harm, claiming that "it were a barbarous thing to hurt the pretty, innocent children". In the following January, the regiment was quartered in
Oxfordshire, where they received a stipend of £252 per week. By the following year,
Edward Hyde, 1st Earl of Clarendon, described Byron as the de facto commander of the Prince of Wales' regiment, although the position was officially held by
Henry Clifford, 5th Earl of Cumberland. Clarendon called Byron a "very valuable and experience officer". In March 1643, at the
Battle of Hopton Heath, the Royalists' commanding officer, the
Earl of Northampton, was killed leading a cavalry attack. Byron led a second charge which overran and captured the enemy artillery, while driving their cavalry from the battlefield. Byron himself was injured, taking a wound to his thigh. After recovering, Byron was given orders to provide support to
Lord Hopton, who after his campaign in the south-west, was preparing to assault Surrey and Sussex. Byron and his regiment joined forces with Hopton in November 1643. ==Death==