Brigadier Gardiner entered the Australian Defence Force in 1995, serving his formative years as an Armoured officer in both junior command and training roles. He has undertaken a range of postings throughout his career, spanning training, staff and command positions.
He is a graduate of the Joint Advanced Warfare School in Norfolk, Virginia, and the Australian Command and Staff College. Key staff appointments include Chief of Staff Special Operations Command, Director Domestic and Regional Plans within Joint Operations Command, and Military Assistant to the Special Operations Commander Australia. Brigadier Gardiner was privileged to serve as Commanding Officer of 1st Armoured Regiment.
During this tenure he led a deployment to Iraq, commanding the Training Task Unit, Task Group Taji. Other operational deployments include a staff appointment within the Multi-National Division South East, Iraq, as the Division Battle Captain, and as a staff officer within Headquarters Regional Command South, Afghanistan, employed as the Divisional Chief of Operations. Brigadier Gardiner holds a Bachelor of Arts in History, a Master of Arts in Strategy and Policy, and a Master of Science in Joint Campaign Planning and Strategy.