Lieutenant Colonel Peter M.R. St. Denis MSC, CD joined the Reserves in 1984 with the 11th Field Regiment, Royal Canadian Artillery, while waiting for a position in the Regular Force and joined 3rd Battalion, The Royal Canadian Regiment (RCR) in 1985. In 1986, while on a United Nations peacekeeping tour in Cyprus, he was awarded the Meritorious Service Cross for his actions in three highly volatile situations. In 1987, with 3 RCR in Winnipeg, Manitoba, he was promoted Master Corporal and in 1989, with 3 RCR in Baden-Baden, Germany, he was promoted Sergeant.

In 1990, LCol St. Denis rejoined the Reserves to begin a career with the Peel Regional Police Service. In 1995, while serving with The Royal Highland Fusiliers of Canada as a Company Sergeant Major, he was commissioned 1st Lieutenant. In December 2000, he joined The Queen’s Own Rifles of Canada and served as Operations Officer, commanded the Parachute Company and 60th Company, and commanded the guard at the official opening of the Juno Beach Centre in France. He also led the burial party for three unknown 3rd Battalion soldiers from WW1, found in the area of Ypres, Belgium.

In 2007, he was seconded to 2 Area Troops in preparation for Task Force 3-08, Op ATHENA, as the Officer Commanding the CIMIC Coy. He received the Land Force Central Area Commander’s Commendation for his work in the repatriation of the soldiers killed in Afghanistan and Lebanon. From August 2008 until April 2009, as Officer Commanding CIMIC within the Provincial Reconstruction Team, he commanded over 100 Reserve and Regular Force soldiers “outside the wire” in Kandahar Province, Afghanistan.

On September 25, 2011 he replaced Lieutenant Colonel John Fotheringham as Commanding Officer of the Queen’s Own Rifles of Canada.

On September 14, 2014, he was succeeded by Lieutenant Colonel Sandi Banerjee.

In May 2015 Lieutenant Colonel St Denis was appointed Commanding Officer of the Argyle and Sutherland Highlanders located in Hamilton, Ontario. He relinquished command after 5 years in May 2020.

Lieutenant Colonel St Denis is a Professor in the Justice and Wellness Studies Program, at Mohawk College, Brantford.