 After leaving Queen’s College, where he was a member of the Queen’s College Cadet Corps, Granger joined the Guyana Defence Force as an officer cadet in 1965 and was commissioned as a Second Lieutenant in 1966.He received his professional military training at the Army Command and Staff College in Nigeria; the Jungle Warfare Instruction Centre in Brazil; and the School of Infantry and the Mons Officer Cadet School, respectively, in the United Kingdom.He became commander of the Guyana Defence Force in 1979 and was promoted to the rank of brigadier.