After the United States entered World War I in 1917, Pope took a job in the Personnel Division of the War Department's General Staff in Washington, D.C. He began lecturing and writing on military morale and on the assessment for promotion of officers. After the war he was among the organizers of the League of Oppressed Peoples and made speaking tours in favor of the Irish Free State. He also intensified his study of Islamic art, a field that was not yet being taught in American universities.