Promoted to colonel on 25 July 1810,[10] Byng went to Spain in September 1811 to become Commander of a brigade serving under General Rowland Hill.[6] Promoted to major-general on 4 June 1813, Byng commanded his brigade at the Battle of Vitoria in June 1813 and then at the Battle of Roncesvalles on 25 July 1813 when his brigade took the brunt of the French assault and held its position for three hours in the early morning before finally being forced back; meanwhile General Lowry Cole rushed up reinforcements in the early afternoon and then fended off the French until the evening when thick fog rolled in.[11] Byng's stubborn resistance at Roncesvalles allowed the Marquess of Wellington (later the Duke) to consolidate enough troops to defeat the French at the Battle of the Pyrenees over the next few days.[2]
Battle of the Nive
Byng also fought at the Battle of Nivelle in November 1813 and then at the Battle of the Nive in December 1813; at the latter battle, he led his troops up a hill under fire, occupied it and then planted the colour of the 31st Regiment of Foot there before driving the French troops down the hill. His conduct was such that the Prince Regent told him that he was
"permitted to wear over the arms of the family of Byng, in bend sinister, a representation of the colour of the 31st Regiment of Foot," and the following crest of honourable augmentation: "out of a mural crown an arm embowed, grasping the colour of the aforesaid 31st regiment, and pendent from the wrist by a ribband the gold cross presented to him by His Majesty's command, as a mark of His royal approbation of his distinguished services".[12]
Byng became General Officer Commanding the Eastern District in England in October 1815[18] before transferring to be General Officer Commanding the Northern District in England in June 1816.[19] At the Peterloo Massacre of 1819, he was absent because he had two horses entered at York races that day, and delegated command to his deputy, who failed to peacefully disperse the large crowd, resulting in 18 deaths and hundreds of injuries.[20] Promoted to lieutenant general on 27 May 1825,[21] he was advanced to Knight Grand Cross of the Order of the Bath in 1828.[15] He became Commander-in-Chief, Ireland and was admitted to the Privy Council of Ireland later that year.[15] After leaving Ireland, he was elected as a WhigMember of Parliament for Poole in Dorset in October 1831[22] and was one of the few military men who supported the Reform Bill of 1832.[15] He was also appointed to the honorary position of Governor of Londonderry and Culmore on 15 June 1832.[23] In recognition of Byng's support for the Reform Bill, the Prime Minister, Lord Melbourne, raised him to the peerage as Baron Strafford of Harmondsworth on 8 May 1835,[24] which territorial designation recognised the Earldom borne by his maternal ancestors which had become extinct in 1799. He was promoted to full general on 23 November 1841,[25] and on 28 August 1847 he was raised further in the peerage as Viscount Enfield and Earl of Strafford[26] Also in 1847, following the death of his eldest brother the Whig MP George Byng (1764-1847), he inherited Wrotham Park.[27]
Secondly, following the death of his first wife, he married Marianne James, a daughter of Sir Walter James James, by whom he had a further son and three daughters.[6]