General Grant joined the Pictou Highlanders in 1951 and transferred to the Mount Allison contingent of the Canadian Officer Training Corps (COTC) in 1953. He became a 2nd Lieutenant in 1955 and served in third phase COTC with the 2nd Canadian Infantry Brigade Group in Germany. He transferred to 1st Battalion Nova Scotia Highlanders in 1957 as a Lieutenant. He held every noteworthy appointment with the 1st Battalion, including Commanding Officer from 1970-1972. He then served as Senior Staff Officer Operations and Training at Atlantic Militia Area Headquarters from 1972-1974.
Upon his promotion to Colonel in 1974, John James Grant became Commander Western Nova Scotia Militia District. In 1977, he became Deputy Commander Atlantic Militia Area and was promoted to Brigadier General and appointed Area Commander in 1980. In 1984, he was appointed Senior Reserve Advisor to the Commander of Force Mobile Command (FMC) and, from 1985-1987, he served as the first Chief of Staff Reserves for the Army (FMC), and the Reserve Council at National Defence Headquarters. In 1987, General Grant was appointed Special Projects Officer on the Chief of Reserves Council at National Defence Headquarters, where he served until his retirement from the Canadian Armed Forces in 1989.
General Grant was appointed as the Honourary Lieutenant Colonel of the 1st battalion, Nova Scotia Highlanders, in 1996, and appointed Honourary Colonel of 1st and 2nd battalions, Nova Scotia Highlanders, in 2004. He served twelve years on the National Council of Honorary Colonels, including two years as Chairman, completing his service in December 2010. During this time, he was actively involved in the Land Force Reserve Restructure process and in Army Reserve Strategic Planning.
During his military service, he was invested as an Officer in the Order of Military Merit in 1979 and as a Commander in the Order in 1988. He has been awarded the Canadian Forces Decoration with three clasps and has over 50 years of dedicated service in the Canadian Armed Forces.
General Grant has been a Governor of the Nova Scotia Division of the Canadian Corps of Commissionaires since 1986, serving as Vice Chair and Chairman of numerous committees. He has served on the National Board, on committees of the National Board and as a member of the National Executive. He completed 25 years of service with the Board in January 2011.
General Grant has also been active in community affairs, serving as President of the Saint Andrews Society, the Festival of the Tartans, the New Glasgow Rotary Club and the Atlantic Building Supply Dealers Association, and as a member of the Military Museum Citadel Hill, the Nova Scotia Home Warranty Advisory, the New Glasgow Police Commission and Downtown Development Association, and the Nova Scotia Army Cadet League. He is a Life Member of the Army Cadet League of Canada, and is currently Honourary President of the Nova Scotia Army Cadet League.
General Grant and his wife, Joan Fraser, have three sons (one deceased), a daughter and five grandchildren.