His textbook, “Medieval History: Europe from the Fourth to the Sixteenth Century,” was widely used for decades. In 1944, the U.S. Army published a paperback edition with a print run of 25,000 copies, for distribution to American soldiers, presumably to facilitate their understanding of European society.

Mediaeval history, Published for the United States Armed Forces Institute by Harper & Brothers, 1944
Imprimatur of General Marshall
Cornell University, Olin Library D117.S83 M4 1944