Dunkellin entered the army in 1846 and was in the
Coldstream Guards. He served as
Aide-de-Camp to the
Lord Lieutenant of Ireland (
Lord Bessborough between 1847 and 1848 and then
Lord Clarendon between 1848 and 1852) and then as State Steward to the Lord Lieutenant (
Lord St Germans between 1852 and 1854). Subsequently, he served in the
Crimean War and was taken prisoner during the
Siege of Sevastopol in October 1854. He was appointed a
Lieutenant-Colonel in 1854, and was awarded the
Order of the Medjidie by
Abdulmejid I,
Sultan of the Ottoman Empire. In 1856, Dunkellin was Military Secretary to the
Viceroy of India, his uncle
Lord Canning, and also served as a volunteer on the staff during the
Anglo-Persian War (1856–57). He retired from the Coldstream Guards in 1860. ==Political career==