When he is a grown man (Antonio Moreno), Ulysses uses his life savings to purchase the Mare Nostrum, a fast, modern freighter, and prospers.

On a stop in Italy, Ulysses visits the ruins of Pompeii, and meets Freya Talberg (Alice Terry) and the learned Doctor Fedelmann.

Ulysses then employs the Mare Nostrum in the service of the Allies, arming her with a deck gun, replacing his crew with French military sailors, and transporting munitions to Salonica.

[2] Rex Ingram's reputation as an outstanding Hollywood director[3] rested on the enormous success of his 1921 The Four Horsemen of the Apocalypse, a film adaption of Spanish novelist Vicente Blasco Ibáñez ’s work that had, according to Kevin Brownlow “made a star of Valentino, saved Metro Pictures from bankruptcy, and earned the director the undying gratitude of the head of Metro, Marcus Loew.”[4] Ingram was determined to adapt another Ibáñez novel, his 1918 Mare Nostrum, “an epic tale of World War I espionage and naval battles.” The title was taken from the Latin term used by ancient Romans for the Mediterranean Sea.

[5] Ingram purchased the former Gaumont studio located in Nice, France, financed by M-G-M preliminary to making Mare Nostrum.

Eventually, technicians had to be brought in from Hollywood for this work.”[7]The film adaptation required location shooting in France, Italy and Spain, obliging Ingram to allot the sequences shot in Barcelona to his cinematographer John F. Seitz.

[8] A highly regarded sequence in Mare Nostrum depicts spy Freya Talberg's execution by German authorities for treason.

No one who saw it could forget the execution at Vincennes, her arrival by limousine, dressed in fashionable clothes (‘I shall die in my uniform’), her lofty bravery quenched by the actual sight of the rifles, her single horrifying glimpse of the coffin waiting to carry her away...Ingram never again equaled this sequence.”[10]From the over one million feet of film Ingram shot, his editing produced a four-hour rough cut.

[11][12][13] “Rex Ingram, a major talent who specialized in big films, was more a painter than a movie director, with little sense of pace and rhythm, [possessing] at best a superb pictorial flair.

[14] Mare Nostrum opened to encouraging critical reviews, though both Motion Picture Magazine and Variety reported that audience response at its premier was unimpressive.

[15] Ingram insisted on retaining the original title from Ibáñez's novel, which some critics and audiences found perplexing (mare is Latin for “sea”, in English, a “female horse”).

[16] Movie-goers of Spanish and Italian descent flocked to the Mediterranean-themed picture at New York's Capitol Theatre, grossing M-G-M almost $20,000 in the first two weeks of its release.

[17] Post-World War I nationalism in Europe polarized the reaction to Mare Nostrum, which depicts a German U-boat destruction of a Spanish merchant ship.