Yugoslavia

In 1995 Leslie was promoted colonel and posted to Yugoslavia as Chief of Staff for Sector South.^[8] He then became the chief of staff and deputy commander of United Nations Confidence Restoration Operation in Croatia.^[8] During the attack of the Croatian forces on the Serbian-held Krajina region, he was credited with leading an operation which resulted in saving lives of 40 civilians.^[10][11]

Brigade

Leslie was the Area Chief of Staff during the Manitoba floods disaster assistance efforts in Spring 1997.^[8] Later that year, he became commander of 1 Canadian Mechanized Brigade Group based across Western Canada. In early 1998, the Brigade Group (reinforced) deployed to the South shore of Montreal to help with the ice storm disaster, and then continued with a series of Battle Group and Brigade Exercises.^[8]

Communications and division command

While participating in both the Advanced Military Studies and the National Military Studies programs in Toronto, Leslie was promoted to brigadier-general in 1999.^[12] Later appointed as the J6 of the Canadian Forces, he commanded the Regular and Reserve communications and Electronic Warfare regiments, and was responsible for the networks operations center and classified communications research establishments.^[12] In 2002 he was promoted commander of Land Force Central Area, later renamed the 4th Canadian Division, responsible for one Regular and three Reserve Brigades, and various supporting bases.^[8] He led the detailed mission reconnaissance in Afghanistan while the Canadian government considered options as to a 9/11 response.^[8]

Afghanistan

As of July of 2003, Leslie was promoted to major-general and subsequently appointed commander of Land Force Doctrine and Training System.^[12] In August of 2003, he was appointed deputy commander of the International Security Assistance Force in Afghanistan, which would later become a NATO mission, working under a United Nations Chapter 7 mandate.^[13] He was double hatted the commander of Task Force Kabul.^[8] Leslie led the mission efforts which focused on stability, counter insurgency, and counter terrorist operations, during which many hundreds of tanks, rocket launchers and heavy artillery were taken away from various warlords.^[14] Upon his return to Canada, Leslie was awarded the Meritorious Service Cross.^[8]

Leslie was then appointed assistant chief of the Land Staff in 2004, and shortly afterwards became the director general of strategic planning at National Defense Headquarters in Ottawa.^[8] In June 2006, he was appointed Chief of the Land Staff.^[15]

Chief of transformation

In June 2010, General Leslie was succeeded by Lieutenant-General Peter Devlin as chief of Land Staff^[16] being appointed Chief of Transformation for the Canadian Forces.^[17] In this position, Leslie was responsible for releasing the 2011 Report on Transformation, which, among other changes, recommended significantly cutting headquarters' budgets and transferring the funds to front line combat units.^[18] Leslie referred to this as transforming the Forces into "more tooth and less tail," a phrase that was used by Prime Minister Stephen Harper and Minister of National Defence Peter MacKay. Some saw Leslie's report as recommending to sacrifice too many sacred cows, namely the bloated headquarters organizations.^[19]

Retirement

Leslie retired in September 2011 after 35 years in uniform and was subsequently hired by CGI Group to lead their new Defence, Public Safety and Intelligence unit in Ottawa.^[20]

Liberal advisor and candidacy

On September 18, 2013, Leslie was named co-chairman of the Liberal International Affairs Council of Advisors, providing advice on foreign and defence issues to Liberal Party of Canada leader Justin Trudeau.^[22][23] Leslie then ran as the Liberal parliamentary candidate in the 2015 general election for the riding of Orléans. He was elected the Member of Parliament for Orléans in the 2015 election ahead of Conservative incumbent Royal Galipeau.^[24]