Tennery was a volunteer and private who left his farm home in Effingham County, Illinois on June 29, 1846, to go to war. The diary covers his long trek down the Mississippi, across the Gulf of Mexico to Matamoros, up the Rio Grande as far as Camargo, then overland and south to Victoria and Tampico. His Fourth Illinois Regiment was then shipped to Veracruz for the march to Mexico City. In the battle at Cerro Gordo he was shot in both legs. Delayed by his wounds, he followed his regiment home and reached Salem on June 30, 1847.

The diary shows Tennery to have been a sensitive, articulate man reacting with perception to the novelties of his experience. He is as deeply moved by the natural beauties of the Mexican scene as by the sufferings and death among his friends and comrades. Before he reached Cerro Gordo he saw only the effects of the fighting, and most of this occurred among a quarreling and badly disciplined American army. Mexican civilians appear frequently in his record, always in terms which suggest friendliness and respect. His pity for their low estate is grounded on his belief that a Spanish tradition has left them priest-ridden.

The introductory sketch of the Mexican War is not altogether satisfactory to a student of Mexican history. The notes are helpful to those interested in the military record of the War.