Dupuy went on to achieve eminence as a military historian and theorist. He is perhaps best known for his very large book The Encyclopedia Of Military History (co-written, like many of his books, with his father R. Ernest Dupuy). In this work Dupuy discusses the world's major and minor military conflicts from the dawn of history to the present day. Entries are arranged chronologically and by region, and most of them give little more than the names of the commanders and (often) very rough estimates for the size of the forces involved in the campaigns. Dupuy was not afraid of expressing an opinion and he classified some of his subjects as Great Captains (such as Alexander the Great, Hannibal, Julius Caesar, Gustavus Adolphus of Sweden, Viscount of Turenne, Frederick II of Prussia and Napoleon). The book mainly describes American and Western European conflicts but offers some coverage of other regions of the world.
