Following the American entry into World War I in 1917, Wanger served with the United States Army in Italy initially in the Signal Corps where he worked as a pilot on reconnaissance missions, and later in propaganda operations directed at the Italian public. It was during this period that Wanger first came into contact with filmmaking. In April 1918 Wanger was transferred to the Committee on Public Information, and joined an effort to combat anti-war or pro-German sentiment in Allied Italy. This was partly accomplished through a series of short propaganda films screened in Italian cinemas promoting democracy and Allied war aims.