Davidson joined the Naval Reserve in 1970 and transferred to the regular forces in 1974 after completing his university studies at the University of King"s College in Halifax. Specialising in navigation and air control, Davidson saw service in the Atlantic and Pacific Oceans, as well as undertaking various staff and headquarters appointments before taking command of HMCS Kootenay in 1989. Davidson remained in command of Kootenay until 1991.
After a posting to the Canadian Embassy in Tokyo, Japan at a military attache, in 1995 he was appointed Commander of Maritime Operations Group Two, with command over a fleet including seven frigates and destroyers and an operational support ship.
In 1997 he was promoted to commodore and took up the post of Direct General Naval Personnel. Between 2002 and 2004 he took command of Maritime Forces Atlantic, which encompassed all Canadian naval forces in the Atlantic—some 8,000 personnel—and oversaw the deployment of ships to the Persian Gulf as part of Operation Apollo, Canada"s contribution to the war in Afghanistan.
In 2004 he was appointed the Canadian military representative to the North Atlantic Treaty Organization Military Committee in North Atlantic Treaty Organization Headquarters in Brussels. He held this post until 2008.
From 2008 to 2011, Davidson served as Canada"s Ambassador to Syria.
In August 2011, he was appointed as Canada"s Ambassador to the Islamic Republic of Afghanistan.