Sent to Europe in March 1917 as an observer, Lieutenant Colonel Billy Mitchell arrived in Paris just four days after the United States declared war and established an office for the American "air service." Upon his arrival in France in June 1917, American Expeditionary Force commanding general John J. Pershing met with Mitchell, who advised Pershing that his office was ready to proceed with any project Pershing might require. Pershing's aviation officer, Major Townsend F. Dodd, first used the term "Air Service" in a memo to the chief of staff of the AEF on 20 June 1917. The term also appeared on July 5, 1917, in AEF General Order (G.O.) No. 8, in tables detailing staff organization and duties. Mitchell replaced Dodd on 30 June 1917, with the position renamed "Chief of Air Service" and its duties described. After Mitchell was superseded in September by Kenly, he remained as "ex officio" chief through his influence on Kenly as Air Commander, Zone of the Advance (ACA).