George B. McClellan was a second lieutenant in the formation of combat engineers that accompanied Maj. Gen. Winfield Scott's army of invasion during the Mexican War (1846 -- 1848). His diary and correspondence written during this period records a rich record of the campaign and offers unique insights into the character of his fellow Engineers; the friction that arose between professional soldiers, officers and men of the volunteer regiments that made up Scott's command; and much about the character of "the young Napoleon," reflecting the talent, the ambition, and the arrogance that characterized the engineer, businessman, soldier, and future politician.

Thomas W. Cutrer is professor of history and American studies at Arizona State University West in Phoenix. He is the author, editor, or coeditor of seven other books, including Brothers in Gray: The Civil War Letters of the Pierson Family, which he coedited with T. Michael Parrish.