In 1900 Dennett enrolled at Bates College, then transferred to Williams College as a sophomore. After his graduation in the spring of 1904 and a year of work in Williamstown, Massachusetts he attended the Union Theological Seminary, where he was awarded a diploma in 1908. He served briefly as a Congregational Minister before leaving to pursue a career in journalism. In 1922 he published Americans in Eastern Asia, a study of American policy in the Far East, which was well received and was long held as an important work in the field. Dennett published "President Roosevelt's Secret Pact with Japan" in 1924, the subject of which came to be known as the Taft–Katsura Agreement. This paper put forth the thesis that formerly isolationist Japan and the U.S. began to carve up their spheres of influence (which would later become world empires) with this agreement, and it was therefore of first-class importance historically. Later historians questioned this interpretation.