During World War II, he served as assistant intelligence officer in the 96th Infantry Division.

Starting in 1948 and continuing throughout the Korean War, Davidson was chief, Plans and Estimates Branch, in General Douglas MacArthur's intelligence office.

It was during this time that occurred one of the US Army's greatest intelligence failures in history - not predicting Chinese intervention in the Korean War.

In that case, the court granted habeas relief to a soldier seeking an honorable discharge as a conscientious objector.

From May 3, 1971, to September 30, 1972, Davidson, then a major general, was the Assistant Chief of Staff for Intelligence, Headquarters, Department of the Army.