Haig was educated at Kensington Grammar School where he competed and won a cadetship offered by Sir Henry Willock who was a director of the East India Company.
He joined the Military College at Addiscombe and graduated third in 1854 after W. Jeffreys and Clement M. Browne.
He returned to India and joined the Rajputana Field Force under General Roberts during the 1857 uprising and was present at the Siege of Kota in 1858.
He then allayed the panic, worked on pumping out the water and fixing the leak and took the steamer until the shore where all passengers were safely able to leave.
Haig was appointed commissioner at the International Congress of Geography held at Venice in 1881.