He served with the British Army during World War I, and upon his return wrote a popular autobiographical book, Over the Top, which sold over a quarter million copies.

He served for six years as a professional soldier in the U.S. Cavalry, during which time he became a first class horse-rider and marksman, and was resident in New York City performing duty as a recruiting sergeant for the New Jersey National Guard when World War I began.

He was also briefly a popular songwriter during the war years, writing the lyrics for hits such as "Your Lips Are No Man's Land But Mine", "Liberty Statue is Looking Right at You", and "Our Country's In It Now, We've Got To Win It Now".

However, the revolution in film-making that took place with the introduction of sound film at the end of the 1920s, combined with the increasing competition in Hollywood as its gathering financial power attracted professional talent able to work in the new audio-visual medium from across the world, spelled the end of Empey's career there, apparently unable to adapt to the new changed environment along with many others from the Classical Hollywood Silent Era.

In the late-1920s, as his Hollywood film career was dwindling, Empey shifted into a new creative direction on being commissioned to write World War I themed pulp fiction stories, creating the character Terence X.

[12] Ernest Hemingway rated Over the Top as "a pitiful piece of bravado writing" but, among the products of propaganda writers of World War I, "the nearest thing to usable material."

[13] On its membership roll was Victor McLaglen (who also possessed his own militia unit at that time called The California Light Horse Regiment), Gary Cooper, Ward Bond, with Ted Parsons as its personnel officer.

In response, Empey confirmed that it was his intention to expand the organization nationally, but denied that it was politically driven or had any sympathy with the Fascist movements that were engulfing the European continent at that time (this had been a charge made by far-left critics).

Empey married Marguerite Andrus, Hollywood actress (professional name Patricia Archer) and former "Miss Long Beach" beauty contest winner, in March 1930,[19] they were subsequently divorced in Los Angeles, in October 1934.