Eyre was commissioned into the 2nd Battalion,
Princess Patricia's Canadian Light Infantry in 1988. In 1993 Eyre, who was a captain at the time, was deployed to Croatia as part of the
United Nations Protection Force. He took part in
Operation Medak Pocket in which he commanded a
reconnaissance platoon, which witnessed the aftermath of
ethnic cleansing in the village of
Lički Čitluk. He became commanding officer of the 3rd Battalion, Princess Patricia's Canadian Light Infantry in 2004. He went on to become commander of
2 Canadian Mechanized Brigade Group in 2009 and, Eyre became the first non-American to serve as deputy commander of the
United Nations Command in South Korea. He was succeeded by Vice Admiral
Stuart Mayer of the
Royal Australian Navy in June 2019, and returned to Canada as Commander Military Personnel Command. On July 12, 2019, it was announced Eyre would be appointed the commander of the Canadian Army, effective from August 20. Eyre was appointed acting chief of the Defence Staff on February 24, 2021, following the stepping aside of Admiral
Art McDonald pending an investigation by the
Canadian Forces National Investigation Service. He was promoted to full
general on August 13, 2021 and appointed as the official Chief of Defence Staff on November 25, 2021. Eyre was made a Commander of the United States'
Legion of Merit on April 24, 2021. in 2020, was awarded an
Oak Leaf Cluster (second award) to the Legion of Merit. On March 15, 2022, Eyre, along with 313 other Canadians, was banned from entering Russia, in protest of the Government of Canada's opposition to the
Russian invasion of Ukraine. ==Honours and decorations==