With the entry of the United States into World War I in April 1917, the operational control of the new U.S. Coast Guard was transferred to the Department of the Navy. Bertholf's responsibilities were to advise the Chief of Naval Operations about U.S. Coast Guard matters and he had administrative control of Department of the Treasury functions within the Coast Guard. An immediate problem he faced was the one-year enlistment period that enlisted personnel served under. Many of the sailors were foreign born and either deserted or were discharged at the end of their enlistment when the war broke out. Others chose to enlist in another armed service where the chances of promotion were better. In 1918 the enlistments were changed to the duration of the war but no longer than three years. The pay and rank differences between Navy and Coast Guard personnel were also a continuing problem for Bertholf during this time and were not completely solved during his tenure as Captain-Commandant. Projects that he had direct supervision over during the war included setting up land communications between shore installations on the Eastern seaboard, enforcement of the Espionage Act of 1917; port security, and establishment of a Coast Guard aviation branch. On 1 July 1918 he was promoted to Commodore, USCG.