 While on duty, del Valle participated as an observer with the Italian Forces during the Second Italo-Abyssinian War.The experiences which del Valle gained as an observer led him to author the book "Roman Eagles Over Ethiopia" where he describes the events leading up to the Italian expedition and the complete movements of combat operations by the Italian Army under Generals De Bono, Badoglio, and Graziani.During the course of his service, De Valle revealed himself to be a fervent admirer of Benito Mussolini.