 Company A served during the Mexican–American War of 1846, participating in the Veracruz campaign and charging up the heights of Chapultepec in Mexico City.During the war, three future Civil War generals, among them George McClellan and P.G.T.Beauregard served as lieutenants in Alpha Company, and the company worked closely with then-Captain Robert E. Lee, an engineer aide to General Winfield Scott.