Cornelius Frances Clery was born in 2 Sidney Place, Cork, Ireland on 13 February 1838.

He became Deputy Assistant Adjutant & Quartermaster-General in Ireland in 1875,[3][4] the same year his book, Minor Tactics was published.

[3][4] In 1878 Clery, now a major, was sent to South Africa as a special staff officer where he served in two brief expeditions in Griqualand West and Sekhukhuneland.

He later took part in the Anglo-Zulu War as the principal staff officer to Colonel Richard Glyn, the man responsible for the centre column of the invasion force.

Then, in the early hours of 22 January, he accompanied Glyn, Lord Chelmsford and half of the column as they were drawn away by a decoy element whilst the camp was massacred during the Battle of Isandlwana.