Ashton was commissioned as a provisional second lieutenant in the 38th Battalion Dufferin Rifles of Canada in 1893.
Promoted to captain in 1895, major in 1902 and lieutenant colonel in 1907, he became Commanding Officer of the Dufferin Rifles that year.
He was appointed Commanding Officer of the 36th Battalion, Canadian Expeditionary Force in 1914 at the start of World War I.
Promoted to brigadier in 1917, he became Commander of 15th Canadian Infantry Brigade that year.
[2] In 1935 he was selected to be Chief of the General Staff and in 1939 he became Inspector-General of Military Forces in Canada.