Early career and regimental command

Gilmore was initially posted to the 8th/9th Battalion, Royal Australian Regiment as a platoon commander, later serving with the Infantry Centre in Singleton, New South Wales, and the 4th/3rd Battalion, Royal New South Wales Regiment in Sydney. In 1988, Gilmore passed selection and was appointed to the Special Air Service Regiment (SASR). For over a decade he filled various appointments in the SASR, including as a troop commander, adjutant, operations research officer, and squadron commander, rising to the command of the regiment in 2001.^[9][11] That year, he was selected as a recipient of the Centenary Medal in recognition of his "service to Australian society through the Australian Army".^[12]

Gilmore's period as commanding officer of the SASR coincided with Operation Slipper, Australia's initial commitment to the War in Afghanistan. The Australian government decided to deploy a Special Operations Task Group, which was to include 1 Squadron SASR under Major Daniel McDaniel. The contingent embarked in October, with Gilmore in command. The Task Group deployed via Diego Garcia and Kuwait to Kandahar Province in southern Afghanistan. There, Gilmore's men worked alongside United States Marines in Brigadier General Jim Mattis's Combined Task Force 45 to eliminate terrorist save havens by disrupting Taliban and Al Qaeda elements in the region.^[13] After more than three months of heavy activity, during which 1 Squadron SASR was involved in intelligence, surveillance and reconnaissance missions,^[14] Gilmore was succeeded in command of the Australian Special Operations Task Group by Lieutenant Colonel Rowan Tink on 1 February 2002.^[15] Three squadrons of the SASR completed operational rotations in Afghanistan over the first twelve months, receiving praise from Mattis and other coalition partners for their efficiency and effectiveness.^[16] The squadrons' achievements were recognised with the Meritorious Unit Citation, while Gilmore was awarded the Distinguished Service Cross (DSC) and the United States Bronze Star Medal.^[17][18] The citation for Gilmore's DSC praised his "distinguished and inspirational leadership" in Afghanistan, noting that he "demonstrated an exceptionally high level of leadership and remarkably fine political acumen."^[19]

Rise to senior command

In 2003, Gilmore was posted to Australian Army Headquarters in Canberra as Director of Strategy and International Engagement. He was soon after seconded to the Department of the Prime Minister and Cabinet, where he spent eighteen months working in the National Security Division. Promoted brigadier in November 2005, Gilmore deployed to Baghdad to lead the Coalition Advisory Support Team in the Iraqi Joint Headquarters. His work supported coalition operations in the Iraq War, including those of the Australian forces deployed on Operation Catalyst;^[7][9][11] he was awarded the Officer of the Legion of Merit from the United States government for his services in the role.^[2] He returned to Australia in 2006 and occupied a series of staff positions at Army Headquarters, including Director General of Defence Public Affairs and Director General Future Land Warfare, and as chief of staff at Headquarters Special Operations Command.^[9] Gilmore's "exceptional service" in these posts led to his appointment as a Member of the Order of Australia in the Queen's Birthday Honours of June 2009.^[20]

Gilmore (left) discusses troop movements with a United States Marine Corps major during a training exercise in the Northern Territory, August 2015.

Gilmore was selected to command the Special Operations Forces assigned to the International Security Assistance Force (ISAF), and redeployed to Afghanistan to take up the role in October 2009. The posting lasted twelve months and, on his return to Australia, he was promoted major general and succeeded Major General Tim McOwan as Special Operations Commander Australia (SOCAUST) in January 2011.^[7][9][11] As SOCAUST, Gilmore was responsible to both the Chief of Army and Chief of Joint Operations for the training, capability development, and operations of Australia's special forces.^[21] In November 2012, Gilmore represented the Australian Army and Special Operations Command during the reinterment of two Australian soldiers at Port Moresby (Bomana) War Cemetery. Both men had been killed while serving with Z Special Unit during the Second World War.^[22]

Gilmore was appointed an Officer of the Order of Australia in the 2013 Queen's Birthday Honours. The award recognised "his outstanding leadership and commitment to Special Operations Command" as SOCAUST and commander ISAF Special Operations Forces.^[23] Three months later, on 20 September, he succeeded Major General Angus Campbell as Deputy Chief of Army.^[11] He occupied the role for sixteen months, before being appointed Commander Forces Command on 23 January 2015.^[24] Based at Victoria Barracks, Sydney, in this role he was responsible for the training, development and sustainment of the bulk of the Australian Army's forces and training establishments, including its infantry and aviation brigades and the Army Recruit Training Centre.^[25] In December 2016, he became Head Military Strategic Commitments Division within the Vice Chief of Defence Force Group,^[26] with purview for the strategic management of potential and present commitments for the Australian Defence Force. He relinquished the appointment and retired in 2019.^[27]