He entered the Royal Military College, Duntroon, in 1947, graduating in December 1951 as BSM (Battalion Sergeant Major or head cadet) and winner of the Sword of Honour.

He was commissioned as a Lieutenant in the Infantry and allotted to 2RAR at Puckapunyal in Victoria. In mid 1952 he was posted as a Rifle Platoon commander in 3RAR on active service in the Korean War. The following year he served in Japan for six months as a Rifle Company commander of the Australian Reinforcement Unit before returning to Victoria, firstly to the Royal Australian Regiment, then briefly as an instructor at the Officer Cadet School, Portsea. In 1955 Captain Hooper was appointed to the staff of Headquarters 3rd Division and later as Adjutant 8/7 Infantry Battalion based in Ballarat. In late 1957 he joined 1RAR in Queensland which was then deployed to North Malaya where he served initially as Adjutant and subsequently, on promotion to major, as a Rifle Company Commander on the Thai border engaged in counter terrorist operations.

Following attendance at the Army Staff College, Queenscliff, he spent two years instructing at the Royal Military College, Duntroon in the subjects of infantry tactics and military writing. In late 1965 he joined 1RAR Group in South Vietnam as Second in Command. 1 RAR Group, which included elements of Armour, Artillery, Engineering and Aviation, was then serving as part of 173rd US Airborne Brigade. Later, upon the arrival of the 1st Australian Task Force at Nui Dat, he became Second in Command of 6RAR. On returning to Australia in 1966 Major Hooper served as an operations staff officer in Army Headquarters. In 1967 he was promoted Lieutenant Colonel and attended the US Marine Corps Command and Staff College.

From 14 September 1970 he commanded 5RAR at Holsworthy until 13 January 1972. This was followed by attendance at the Australian Joint Services Staff College in Canberra. His next appointment was as an analyst in the Joint Intelligence Organization, also in Canberra. In 1974 he was promoted Colonel to become The Military Secretary, a position broadly responsible for the management of officers. He was then promoted Brigadier to be Director General of Personnel Operations, which embraced a wide range of personnel policy matters for the Army. He spent a year as Deputy Chief of Personnel and then in December 1982 Brigadier Hooper was appointed Commander of the 2nd Military District, a position he held until his retirement from the Army on 14 February 1984.

He was awarded the CBE (Commander of the British Empire) on 1 January 1983.

In summary, during his 37 years in the Army he served in five infantry battalions of the Regiment: 2RAR (Puckapunyal), 3RAR (Korea), 1RAR (Malaya), 6RAR (Vietnam) and 5RAR (Holsworthy). Three were on active service.

He died at Dalmeny on the south coast of NSW on 1 August 2007 at age 78.

Brigadier John Hooper CBE will be remembered as a principled gentleman, a strong leader and an outstanding soldier who gave his all to the Regiment and the Army.