In addition to going on to earning great laurels or garnering much notoriety in the American Civil War, all of these men had another thing in common: they were all graduates of the United States Military Academy and were, thus, all regular army officers. Yet, of the nearly 100,000 men who served in Mexico, only about twenty-five to thirty percent—some 25,000-30,000 soldiers—were Regulars. The rest were volunteers.
Volunteer units hailed from twenty-four of the nation’s twenty-eight states as well as from the District of Columbia; Iowa and California, which at the outbreak of hostilities had yet to achieve statehood, also furnished troops. In all, between 70,000 and 75,000 volunteers, comprising the ranks of 76 regiments and several additional companies, enlisted during the war. Thousands of these men would later serve in both the blue and the gray during the Civil War. And because of their former military experiences in Mexico, most would enter America’s sectional conflict as commissioned officers primarily at the regimental level, being mustered in as lieutenants, majors, or colonels, and subsequently rising through the ranks. Take, for example, C. Roberdeau Wheat. Before organizing the famed Louisiana Tigers in 1861 and falling dead while leading his regiment at the battle of Gaines’s Mill in June 1862, the 6’4” Wheat served as captain of the Tennessee Company of Mounted Volunteers in Mexico. His is just one of countless examples of volunteer officers who served in both the Mexican and Civil Wars.
Of the thousands of Mexican-American War volunteers who would later serve in the Civil War, more than sixty would become general officers during the latter conflict. This number does not include West Point graduates who served in volunteer organizations in Mexico and as generals in the Civil War, men such as Jubal Early, Henry Naglee, Samuel R. Curtis, Lloyd Tilghman, Goode Bryan, and Humphrey Marshall. Instead, the Mexican War volunteers who later became Civil War generals, for the most part, lacked a formal military education, but exhibited an avid interest in martial endeavors and were typically members of a local militia company. And they were those who willingly left their civilian lives behind twice to serve in uniform.
Benjamin McCullough, Colonel, Mounted Company, Independent Texas Volunteers
Thomas Green, Captain, 1st Texas Mounted Rifles