Of all our country’s “forgotten wars,” there are none as important to the shaping of the United States as the Mexican-American War of 1846-1848. At the time it was our most divisive war, and many Americans, including many of the officers and enlisted men who fought in the war, considered it to be, in the words of Ulysses S. Grant’s memoirs, “…one of the most unjust ever waged by a strong against a weaker nation.”

But it was perhaps the most successful of all American wars. As Grant also wrote in his memoirs, “The men engaged in the Mexican War were brave, and the officers of the regular army, from highest to lowest, were educated in their profession. A more efficient army of its number and armament I do not believe every fought a battle.” At the end of the war, the United States was 1.2 million square miles larger than it had been before the war, and the victorious United States Army was perhaps the most confident, and experienced, fighting force of its time.

This may well have been a tragedy for America, because the officers who served together and learned and honed their military skills together in Mexico ended up fighting each other with deadly efficiency in the Civil War. Among the Civil War generals who served as lieutenants and captains in Mexico were George Mead, James “Pete” Longstreet, Thomas Jackson (not yet nicknamed “Stonewall”), George Pickett, William Tecumseh Sherman, George McClellan, P. G. T. Beauregard, Braxton Bragg, Ulysses S. Grant—and Robert E. Lee.

Usually, when we think of Robert E. Lee we picture a dignified white-bearded figure, a gray-clad general on a white horse commanding a large conventional army. But that is a picture of General Lee in the Civil War. In the Mexican War, Robert E. Lee was a forty-year-old captain in what was then considered the elite branch of the Army—the Corps of Engineers—and instead of his later white beard, he wore a roguish dark mustache. His father, Henry “Light Horse Harry” Lee had been one of the most famous military commanders of the Revolutionary War, but something of a failure in civilian life.

Robert E. Lee. Photo courtesy of biography.com.

Robert Lee had hardly known his father, but his father had left him quite a military legacy, and he had already begun to make his own reputation when he graduated second in his class from the United States Military Academy without having received even one demerit in the process—a record that is said to be still unbroken. Lee had enjoyed an excellent reputation since his cadet days. He quickly established himself as a military engineer with expertise in fortifications, road and bridge building, artillery emplacement, surveying, and cartography.

He had also shown a good hand at civil engineering, having once helped adjust the Mississippi River to bring it back to its original course somewhat closer to St. Louis. Strangely, Lee did not made rank quite as fast as many of his peers. But as a lieutenant he had made an excellent impression on the Army’s most senior officer, Major General Winfield Scott (aka “Old Fuss ‘n Feathers”). Shortly after arriving in Mexico, Robert E. Lee did such a stellar job running dangerous and crucial reconnaissance missions for General John Wool prior to and during the battle of Buena Vista that when he was preparing to capture the historic Atlantic port city of Vera Cruz, General Scott had Captain Lee assigned to his staff.

On the 7th of March, 1847, in a move that would now seem downright irresponsible (if admirable), General Scott insisted on a firsthand look at the beaches where the Navy proposed to land his troops. With the commander of the naval landing force, Commodore Donald Conner, General Scott set out in a small ship to sail close to shore for a visual recon. Along with him, General Scott took a few of his best staff officers, including Joseph E. Johnson, P.G.T Beauregard, and the two future commanders of opposing armies at Gettysburg, George Meade and Robert E. Lee. The ship came under dangerously close fire from Mexican positions ashore, and while Lee’s thoughts on the matter are unknown, George Meade wrote home that one shot hitting the ship could have ended the whole expedition. This short shipboard jaunt was not Robert E. Lee’s first reconnaissance mission in Mexico, and it wouldn’t be his last.

The landings were successful, and a combined siege and artillery battle followed. Once again, Lee found himself working with the Navy. General Scott was short of heavy artillery ashore, and Commodore Conner agreed to lend him six of his heaviest guns—weighing 6,300 lbs each—but he also specified that Navy gunners accompany and man the guns. Captain Lee was given the mission of covertly moving the terribly cumbersome guns, their equally heavy loads of shot and powder, and their Navy gun crews across exposed sands and over and through thick chaparral to a position that had been surveyed and selected on an earlier reconnaissance. Lee supervised the emplacement of the guns, and then turned command over to a Navy gunnery officer and returned to his staff duties. This arduous feat was accomplished without alerting nearby Mexican forces, who remained unaware of the guns until those guns most devastatingly joined in the fight.