Crimean War

In May 1855, he left for the Crimean War, in which he served firstly with his battalion, then as aide-de-camp from July 1855 to the commander of the 2nd Division, Lieutenant-General Edwin Markham, and finally as deputy assistant quartermaster general from November 1855 on the staff at Headquarters, being promoted to brevet major. He was mentioned in dispatches and received the fifth class of the Turkish Order of the Medjidie and the British, Turkish and Sardinian Crimean medals.^[1][2]

Indian Rebellion of 1857

In 1857, he was promoted to captain and lieutenant colonel, and transferred (1858), as a lieutenant colonel, to the 95th (Derbyshire) Regiment of Foot, serving with that regiment at the end of the Indian Rebellion, for which he was again mentioned in dispatches. He served as deputy adjutant general to the forces in Bombay from 1861 to 1862, and was promoted to brevet colonel in 1863. There, he befriended the then governor of Bombay, Sir Henry Bartle Frere, and this relationship would be important later when serving in South Africa. He served, again as deputy adjutant general, in the 1868 Expedition to Abyssinia, for which he was appointed a Companion of the Order of the Bath and made an aide-de-camp to Queen Victoria in 1868. He was Adjutant-General, India from 1869 to 1874.^[1][2]

Thesiger returned to England in 1874 as colonel on the staff, commanding the forces at Shorncliffe Army Camp, and was appointed to command a brigade at Aldershot, with the temporary rank of brigadier general, in 1877. He had however requested a posting overseas in order to benefit from the cheaper cost of living.^[1][2]

Anglo-Zulu War

Lord Chelmsford sketched by another officer at the Battle of Ulundi

Defeat at Isandlwana

Thesiger was promoted to major general in March 1877, appointed to command British forces in the Cape Colony with the local rank of lieutenant general in February 1878, and in October succeeded his father as 2nd Baron Chelmsford. He brought the Ninth Cape Frontier War to its completion in July 1878, and was made a Knight Commander of the Order of the Bath in November 1878. His experiences fighting against the Xhosa created a low opinion of the fighting capabilities of African soldiers, which later led to disastrous consequences during the Anglo-Zulu War.^[1][2]

In January 1879, the official Sir Henry Bartle Frere, a personal friend of Chelmsford, engineered the outbreak of the Anglo-Zulu War by issuing the Zulu king Cetshwayo an ultimatum to effectively disband his military. Cetshwayo refused this ultimatum, an act which led to an outbreak of war between the British Empire and the Zulu Kingdom. A British expeditionary force under the command of Chelmsford invaded the Zulu Kingdom, heading in three columns towards the Zulu capital, Ulundi. The force was attacked by a Zulu force at Isandlwana, during which the Zulus overran and destroyed the central column of Chelmsford's separated forces. The engagement was an unexpected victory for the Zulus, which threw British war plans into disarray.^[3][4][5]

Afterwards, the British government, anxious to avoid the Zulus threatening Natal, issued orders for the hasty relief of Chelmsford of his command and for him to be replaced with Sir Garnet Wolseley.^[6] However, this order could not be implemented until the arrival of Wolseley, and in the meantime Chelmsford ignored diplomatic overtures from King Cetshwayo^[7] and made plans to capture Ulundi, aiming to defeat them in a decisive engagement and salvaging his reputation before Wolseley's arrival.^{[lower-alpha 2]} The Battle of Ulundi took place on 4 July 1879, being the last major battle of the Anglo-Zulu War. After a half-hour bombardment by the Royal Artillery, Chelmsford attacked a Zulu army massed at Ulundi, making full use of concentrated small arms fire from Gatling guns and rifles, leading to the destruction of the Zulu force. The British Army's casualties after the sharp but brief engagement was ten killed and eighty-seven wounded, in exchange for nearly sixty times that number of Zulu dead. Hall 1978 quotes the London Standard reporting 473 counted dead and another 1000 or more wounded. Chelmsford ordered Ulundi to be burnt, after which he handed over command to Wolseley on 15 July at the fort at St. Paul's and left South Africa by ship for England two days later. The defeat of the Zulus at Ulundi allowed Chelmsford to partially recover his military prestige after the disaster at Isandlwana, and he was honoured as a Knight Grand Cross of Bath.^[8] However, he was severely criticised by a subsequent enquiry launched by the British Army into the events that had led to the Isandlwana debacle,^[9] and did not serve in the field again.^[10]

Later career

Lord Chelmsford became lieutenant general in 1882, Lieutenant of the Tower of London (1884 until 1889), colonel of the 4th (West London) Rifle Volunteer Corps (1887), full general (1888), and colonel of the Derbyshire Regiment (1889). He exchanged the colonelcy of the Derbyshires for that of the 2nd Life Guards (1900), and as such was Gold Stick in Waiting during ceremonial events at Court. King Edward VII appointed him Knight Grand Cross of the Royal Victorian Order (GCVO) in the November 1902 Birthday Honours list,^[11][12] and he was invested with the insignia by the King at Buckingham Palace on 18 December 1902.^[13] He was the inaugural Governor and Commandant of the Church Lads' Brigade, a post he retained until his death.^[1]

Funerary monument, Brompton Cemetery, London