George was born into a Protestant Ulster-Scots family at Trincomalee, Ceylon, on 17 March 1804, and was later educated at Foyle College in Derry. Both his parents were from Ulster, the northern province in Ireland, his father being from Coleraine in County Londonderry while his mother, Letitia Knox, was from County Donegal. His middle name, St Patrick, derived from his birth on St Patrick's Day. In 1819 he entered Addiscombe Military Seminary, on 5 May 1821 was appointed a cavalry cadet, on 15 January 1822 joined the Second Bengal Light Cavalry in Bengal, and on 5 September 1825 was promoted to be adjutant of his regiment, a post he held until September 1834. With his regiment he took part in the Afghan War of 1838, and was present at the storming of Ghuznee (modern Ghazni) on 23 July 1839, and in the attempt to capture Dost Mohammad Khan in his flight in August through the Bamyan pass.