His disinclination for studies led his family to purchase him a commission in the Rifle Brigade in 1825; in 1833, he obtained a captaincy in the Connaught Rangers.
During the Siege of Sevastopol, Shirley supervised a successful attack on the Quarries in front of the Great Redan and received the CB and command of a brigade.
True to his mother's prediction, he was "very idle" in college, and she withdrew him in November 1824 to send him into the British Army, in which his brothers Charles and William were officers.
[6] On 5 July 1833, Shirley purchased a captaincy on the unattached list,[8] and then paid to exchange as a captain into the 88th Regiment of Foot (Connaught Rangers), with whom he would serve for the rest of his active career.
[9] He reported to the Rangers' depot at Sheerness on 15 January 1834, and was stationed with them in England and Ireland until 1836, when the regiment was ordered to the Mediterranean.
Shirley was promoted to lieutenant-colonel on 18 January 1848 and took command of the regiment, after Phibbs died of yellow fever in Barbados.
[15] Under Shirley's command, the Connaught Rangers showed remarkably good discipline, largely free of crime and drunkenness.
[16] On 2 April 1854, the Connaught Rangers, then quartered in Preston, Lancashire, were ordered to march for Liverpool and take ship for the theatre of war on the Black Sea.
[21] During the Siege of Sevastopol, Shirley, as general officer commanding the trenches, prepared the attack of 7 June 1855 upon the "Quarries", a line of rifle pits lying before the Great Redan.
During the attack, a round shot hit the parapet of the trench directly in front of him and blasted his face with sand and gravel, temporarily blinding him.
[32] Shirley was appointed a colonel on the staff in Great Britain on 8 March 1856, commanding troops in Monmouthshire and South Wales.
[40] Shirley was made a Knight Commander of the Order of the Bath in the 1869 Birthday Honours,[41] and on 3 February 1870, he was appointed colonel of the 61st Regiment of Foot.