MacArthur has been regarded as the Army's first press officer

Another interesting fact is that MacArthur has been regarded as the Army's first press officer. On December 11, 1915, MacArthur returned to the War Department and was promoted to major. He was appointed head of the Bureau of Information in the office of Secretary of War Newton D. Baker in June 1916. Since then, MacArthur has been considered the Army's first press officer. Following Germany's declaration of war on 6 April 1917, Baker and MacArthur obtained permission from President Wilson to utilize the National Guard on the Western Front. To minimize the appearance of bias toward any specific state, MacArthur advised sending first a division composed of units from other states.

Baker authorized the formation, which became the 42nd ("Rainbow") Division, and named Major General William A. Mann, head of the National Guard Bureau, as its commander; MacArthur served as its chief of staff, with the rank of colonel. This appointment was given to the infantry rather than the engineers at MacArthur's request. The 42nd Division was formed in August and September 1917 at Camp Mills in New York, where it was trained for open-field fighting rather than trench warfare. On October 18, 1917, it sailed in a convoy from Hoboken, New Jersey, to France. Major General Charles T. Menoher took over as division commander on December 19.