Prior to this, the men of the squadron had spent several weeks at various recruiting barracks around the country, and were brought to Kelly Field in August, before the formal organization of the unit.

The men lived in tents and messed in the open, having to contend with the heat, wind and dust of the late Texas summer.

An outbreak of measles struck the squadron at Post Field, and it extended the amount of time that would normally be spent at the station.

Finally on 16 February, the men of the squadron were examined for overseas duty and were ordered to prepare for service in France.

After receiving equipment, it moved to the Port of Entry, Hoboken, New Jersey, on 5 March and boarded the RMS Cedric, a White Star Liner impressed into troop ship duty.

The training the squadron had received in the United States enabled it to make a valuable contribution to the wing's activities.

The entire 5th Pursuit Group was ordered to Coblenz, Germany, to become part of the Third Army Air Service.

[7] The entire air service of the Third Army, except that of the III Corps Observation Group at Weißenthurm Airdrome, were relieved from further duty, on 12 May 1919 and ordered demobilized.

[7] Personnel at Colombey were subsequently assigned to the commanding general, services of supply, and ordered to report to one of several staging camps in France.

There, personnel awaited scheduling to report to one of the base ports in France for transport to the United States.

[8] The 138th Aero Squadron arrived in New York Harbor in late July after which it was sent to Mitchell Field, Long Island, where it was demobilized in August 1919.