He was adjudged the best in order of merit and awarded the Military Cane at the Ghana Military Academy.

After passing out of the Academy, he was posted to the Armoured Reconnaissance Regiment, Gondar Barracks in Accra as a Second Lieutenant.

He rose through the ranks to become the Chief of Army Staff (COAS) in March 2020, holding the positions of the General Officer Commanding, Southern Command of the Ghana Army, and the Chief of Staff at the General Headquarters for a year.

Other appointments held by the new CDS in the course of his career, include the Aide-de-Camp (personnel assistant )to the Chief of the Army Staff and Chief of the Defence Staff, Ghana Armed Forces and Operations/Training Officer, 64 Infantry Regiment where he rose to become the Commanding Officer with an additional appointment as Commanding Officer for the Armoured Reconnaissance Regiment.

He was also the Coordinator of State Transport Security and an Instructor for the Disaster Management Course, Army Combat Training School in Teshie.

He also held the position of Director of Strategic Intelligence Assessment of the Defence Intelligence Department, General Headquarters and Director Operations and Plans, Defence Industries Department, General Headquarters, amongst many others.

Major General Oppong-Peprah has undertaken several career progression courses. He is the first and the only Ghanaian military officer to have attended the Combined/Joint Forces Land Component Commanders Course at the USA Army War College, Carlisle, Pennsylvania.

He is also a graduate of the prestigious Royal College of Defence Studies in London, United Kingdom and pursued his Senior Intelligence Course at the Joint Intelligence Centre in Strasbourg, France.

He also studied Law of Combating Terrorism at the Defence Institute of International Legal Studies at Newport, Rhode Island, USA and pursued his Senior Command and Staff Course at the United States (US) Army Command and General Staff College at Fort Leavenworth, Kansas, USA.

Other career progression courses undertaken by him include the Senior Command and Staff Course at Ghana Armed Forces Command and Staff College, in Teshie, the Junior Command and Staff Course at the Command and Staff College, Kaduna, Nigeria where he won the Best Allied Student Award and Armour Officer Basic Course at the US Army Armour SchoolFort Knox, Kentucky, USA.

In peacekeeping operations, Maj Gen Oppong- Peprah has served as Humanitarian Officer on the United Nations Assistance Mission in Rwanda, as a Military Observer in the United Nations Aouzou Strip Observer Group in Libya and Chad, a Detachment Second-In- Command/Troop Leader on the United Nations Interim Force in Lebanon/Israel in 1987, 1989 and 1992, respectively.

He was a board member of the Governing Council of the National Disaster Management Organisation (NADMO) for three years. He is married with five children.