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On the morning of Sept. 10, 1847, as dawn broke over the Mexican village of San Ángel, a detail of U.S. soldiers entered a large stone cell, unchained 23 men—most of whom were Irish nationals—bound their hands and marched them outside to the prison courtyard. Hundreds more soldiers stood at attention around a 14-foot-high wooden scaffold, from which dangled a line of nooses. Behind the troops stood a large crowd of villagers, some weeping, others raising crucifixes and rosaries. A court-martial had found the prisoners guilty of desertion. Those 16 who had deserted after the May 1846 U.S. declaration of war on Mexico were to hang, while the remaining seven were each to receive 50 lashes on the bare back from a cat-o’-nine-tails—a rawhide whip with a hard knot at the tip of each of its nine 18-inch thongs. The seven were then to be branded with a red-hot iron on their cheeks with the letter “D.”

In command of the morning’s activities was Brig. Gen. David E. Twiggs, a veteran of the War of 1812, the Seminole wars and the Black Hawk War. Contending it would confer too much honor on the prisoners to be flogged by Regular Army sergeants, Twiggs brought in a Mexican muleteer—a teamster whose profession called for the skilled use of the whip—to deliver the punishment.

Twiggs looked upon one of the prisoners with singular hatred and reportedly promised to pay a bonus to the muleteer if the man were to die under the lash. John Riley, Irish immigrant, former U.S. Army private and the object of Twiggs’ fury, had led these men and some 200 other defectors into battle against the United States under the green flag of the Batallón de San Patricio (Saint Patrick’s Battalion). They had, in the words of one contemporary, “fought like devils” in the service of Mexico, and despite protests and petitions imploring mercy, Maj. Gen. Winfield Scott had decreed that they and dozens of their captured comrades suffer the full weight of the Army’s retribution.

Each of the seven prisoners sentenced to be flogged and branded was tied to a tree as his doomed mates looked on. The teamster measured the distance before swinging his knots against the men’s backs. Twiggs, who sat on his horse slowly calling out the number after each stroke, supposedly miscounted during Riley’s punishment, adding nine strokes to the 50. As the sickening smell of the brandings permeated the courtyard, Twiggs noted that the “D” burned into Riley’s face had been applied upside down and ordered the process repeated correctly on his other cheek. Twiggs then ordered the prisoners’ heads shaved.

Soldiers revived the seven sufficiently to dig graves for their condemned comrades. Then, to the strains of a fife playing the “Rogue’s March,” their guards marched them back to jail to languish in chains until war’s end.

nativism greets irish immigrants arriving stateside

The odyssey that prompted the wholesale desertion of so many men and the formation of the San Patricios began across the Atlantic years before. In the early 1840s hopelessly depressed social and economic conditions in Europe sent a flood of immigrants to America’s shores. While many came in search of opportunity, others sought simply to escape starvation and pestilence.

The people of Ireland had long suffered from hunger and disease, but by the mid-1840s the country had entered the Great Famine. A fast-spreading fungal organism had devastated the potato crop, long a mainstay of the Irish diet for a majority of the island’s population. Absentee British landlords did little to aid their starving tenants, continuing to market grain crops abroad while evicting poor tenants and consolidating plots for rent to those able to pay. In Ireland starvation and its dreaded side effects—scurvy, cholera, typhus, dysentery—killed up to a million people over the next several years and drove some two million more to new lives in England and North America.

For more than two centuries before the Great Famine, Ireland’s young men, facing a hopeless situation at home, had been leaving their native land to fight in the service of foreign armies. These exiles, known as “Wild Geese,” donned the uniforms of Spain, France, Italy, Austria, Germany, Sweden, Poland, Russia and even the hated British empire. When Arthur Wellesley, Duke of Wellington, defeated Napoléon Bonaparte at Waterloo in 1815, perhaps a third of his troops were Irish.

John Riley left County Galway as a teen and enlisted in the British army, rising to the rank of sergeant of artillery. When his term of service ended, Riley immigrated to America, where he and thousands like him enlisted in the U.S. Army. The alternative—for which they would have had to compete with free blacks —was to work as porters, longshoremen, street sweepers or the like. For young men, especially veterans, the Army was—at least on the surface—the better choice.

Their timing couldn’t have been worse. A “nativist” anti-Catholic movement was sweeping the country, born of fear and hysteria. Since the 1820s American-born Protestants had been warning of a “Papist plot” to take over the country. Fire-breathing speakers and clergymen inspired like-minded Americans across the country to commit violence against Irish and German Catholics. In 1844 armed nativist mobs rampaged through the Catholic neighborhoods of Philadelphia, burning several churches, a seminary, a fire station and dozens of Irish homes, leaving at least 30 dead and 150 injured.

Some of the most rabid nativists were in the Army’s officer corps, a Protestant fraternity composed largely of recent West Point graduates who had never seen combat. They especially despised the Irish enlistees. As they saw it, these “bog-trotters” bore no kinship to the true Anglo-Saxon American soldiers who had stood together at Lexington and Concord. Stated one historian, they believed “that any influx of new Irish-Catholic immigrants into the nation’s regiments would sully the American character of the ranks.” There would be no equal treatment for Catholics, and this included German soldiers as well as Irish.

mexican army says irish need apply

The general thinking among Americans of the period, as embodied by a national philosophy recently dubbed “Manifest Destiny,” was that the United States enjoyed the God-given right to expand westward, constrained only by the limits of the ocean. This placed Mexico and its vast possessions in the Southwest directly in the path of American expansionism. Ironically, this came at a time when the Army most needed new recruits. In 1845 America’s peacetime Army, comprising fewer than 9,000 men, was scattered across the continent among more than 100 posts. Despite fierce nativist protests in Congress and the newspapers objecting to recruiting “Papists” into the Army, Irish and German enlistments swelled the ranks.

Having endorsed the annexation of Texas into the Union—a step the Mexicans had warned would lead to war—incoming President James K. Polk set his sights on California and the other Mexican territories. The Philadelphia Nativist newspaper embodied the prevailing mood when it trumpeted, “Providence intended the New World for the Anglo-Saxon. If Mexico should oppose the decree of Heaven—so much the worse for Mexico!” Polk bullied Mexico into a position that offered only two choices: fight or concede. At first Mexican President José Joaquín Herrera attempted conciliation, but his people bristled at his weak stance.

An August 1845 editorial in The New York Herald proclaimed, “The multitude cry aloud for war!” and Polk was fully disposed to accommodate them. In March 1846 the president lit the fuse by sending a force of American troops under Brig. Gen. Zachary Taylor into the disputed zone between the Nueces and Rio Grande rivers. In late April a large Mexican cavalry unit attacked a patrol of American dragoons, killing 11 U.S. soldiers and capturing dozens more. In early May, after calling for reinforcements, Taylor handily defeated the Mexicans at Palo Alto and Resaca de la Palma.

On May 11 Polk addressed Congress, painting America as the innocent victim: “The cup of forbearance had been exhausted even before the recent information from the frontier.…But now, after reiterated menaces, Mexico has passed the boundary of the United States, has invaded our territory and shed American blood upon the American soil.” Two days later Congress declared war on Mexico.

As inducements to enlist, Army recruiters promised humane treatment and ample opportunity for advancement; they lied. In reality the U.S. Army of the mid-1840s was a harsh venue for any enlisted man. Punishment for even the most minor infraction was stringent. During his travels through Texas and Mexico between 1846 and 1852 French missionary Emmanuel Domenech was stunned to witness officers suspending soldiers by their arms from the branches of trees for drunkenness, while others accused of insobriety were bound and then repeatedly thrown into a river and dragged back ashore. Abbé Domenech wrote of one soldier in such despair at the hardships of Army life and brutality of his officers that he cut his own throat with a razor. Flogging was not unusual, nor was branding for excessive drinking. Officers had the letters “HD,” for “habitual drunkard,” burned onto offending soldiers’ foreheads.

While officers frequently used the flat of their swords to punctuate their orders, there was no guarantee they would not employ the sharp of the blade. One infantry private from Pennsylvania wrote in a letter home, “Tonight on drill an officer laid a soldier’s skull open with a sword, and the poor man is now suffering from it in the hospital in camp.”

Officers were generally free to impose whatever form of corporal punishment they chose, without fear of repercussion. One young officer in the Mexican War, Braxton Bragg, was reportedly so unpopular for his harsh disciplinary methods that his men twice tried to kill him. He survived both attempts and went on to become a Confederate general during the Civil War.

Irish volunteers had left their native land in part to escape abusive treatment by the Anglo-Saxons who owned and controlled their own country. At the outset of the Mexican War they faced brutality at the hands of Anglo-Saxon officers and were expected to invade a nation of largely fellow Catholics who dared stand in the way of the United States’ grandiose plans of expansion.

The Mexican high command, aware of the discontent among their fellow Catholics in the U.S. Army ranks, sought to take advantage of the situation. They surreptitiously scattered leaflets among the American troops, promising fair treatment, as well as property, payment and citizenship. The pamphlets played upon the fact that Mexico was a Catholic country, in which a deserter’s religious practices would be not just tolerated but encouraged. Increasingly, the immigrant soldiers of the U.S. Army saw “taking leg bail” to Mexico as an alternative to suffering the ceaseless abuse of their superiors.

Desertion during the Mexican War was rampant. Owing to the flood of enlistments, the number of Regulars facing the Mexicans would swell to some 40,000 by war’s end; of these, 5,331, or 13 percent, would desert. Nearly one-fifth were Irishmen, followed next in percentage by Germans. While a number of these men simply disappeared into Mexico, hundreds joined the Mexican army.

riley’s luck runs out

Riley was among those who switched uniforms. Though he had been a skilled gunner in the British army, he anticipated little chance of commanding an American artillery battery. One night in mid-April 1846, “on the advice of [his] conscience,” he swam the Rio Grande to join the Mexican ranks in Matamoros. Riley, who had come to view the invasion of Mexico as “an unholy war,” did not consider himself a traitor to the United States, never having thought of himself as an assimilated American. In his mind he remained an Irishman.

Based on Riley’s military experience the Mexicans commissioned him an officer. As events soon bore out, it was a wise decision; Riley proved an exceptional artilleryman and a natural leader. Mexican commander Antonio López de Santa Anna, recognizing that his army was lacking in both knowledge and training in the use of cannon, ordered Riley to “raise an artillery company organized from the deserters of the invaders.” Riley accordingly turned a disparate group of foreign nationals and fellow deserters—mainly Irish and German—into a first-rate artillery company. Dubbed the Legión Extranjera (“Foreign Legion”), the single company quickly became two. By presidential order the units comprised a 204-man battalion—142 of whom, by Riley’s count, were Irish— which came to be known as the Batallón de San Patricio.

The San Patricios fought with a skill and fury that astounded and dismayed the American forces. So accurate was their artillery fire that many on the American side accused them of deliberately targeting their hated former officers. Between May 1846 and April 1847 they employed their guns with terrible effect at Matamoros, Monterrey, Buena Vista and Cerro Gordo. After each battle the San Patricios carried their wounded comrades from the field rather than leave them to the gallows if captured. Riley always managed to restore gaps in the ranks with new defectors.

Word of the San Patricios reached the United States, and “the notorious Riley” soon became one of the two most hated men among Americans—the other being the enemy commander and, by then, nine-time president of Mexico, Santa Anna—the same Santa Anna who a decade earlier had ordered the massacres of hundreds of Texians at Goliad and the Alamo.

The end for Riley’s battalion came at the Aug. 20, 1847, Battle of Churubusco when Santa Anna ordered the San Patricios and some 1,200 Mexican troops to hold a fortified convent against numerically superior American forces, thus allowing the commander time to escape with the bulk of the Mexican army. With little left to lose, Riley’s gunners wreaked havoc on the Americans.

Though enemy fire soon destroyed two of Riley’s five guns, his men continued to fight, even as their Mexican comrades sought to surrender. Three times the Mexican officers raised a white flag, only to have it torn down by Riley’s men. Finally, their powder and ammunition gone, the hopelessly outnumbered San Patricios surrendered. Their losses were heavy; a full 60 percent of their number had been killed or captured. Eighty-five men of the Saint Patrick’s Battalion were taken prisoner, Riley among them.

Some of the San Patricios— including Riley—were tried before a court-martial at San Ángel, the others at Tacubaya. In all, 50 were sentenced to die by hanging and another 15 to be flogged and branded. The task of overseeing the executions of the 30 men at Tacubaya sentenced to hang was assigned to perhaps the most ardent nativist officer in the entire U.S. Army. Colonel William S. Harney was a vicious man at the best of times. In St. Louis he had beaten a black female slave to death and fled prosecution. He had summarily hanged captured Indian warriors during the Seminole War in Florida, and he took great pride and pleasure in his proficiency with the rope. Scott, who had previously court-martialed Harney for “unmilitary conduct,” abhorred the man but saw in this “right-hard hater” the perfect vehicle to discourage desertion.

Harney devised a sadistic end for the 30 condemned San Patricios. At first light on September 13 he had the men bound hand and foot and driven on mule carts to a rise outside the village of Mixcoac, atop which he’d ordered erected a long scaffold. There guards forced them to stand in the carts, a noose encircling each neck, and face Chapultepec Castle, where the decisive battle would soon be fought. Harney’s order of execution stipulated the condemned would stand facing the smoke and fire until U.S. forces triumphed. Only then would they die.

Around 9:30 a.m., a few hours into the battle, cheers rose from inside the castle as the American flag rose above the ramparts. With death only seconds away the doomed men cheered as well—a last defiant cry—for Ireland, for Mexico, for the San Patricios. As one Irish-born 2nd U.S. Artillery gunner watching the executions recalled: “What must have been the feelings of those men when they saw that flag—for they knew their time had come! But on the other hand, a cheer came from them which made the valley ring.” At Harney’s order the carts pulled away.

For further reading Ron Soodalter suggests The Rogue’s March: John Riley and the Saint Patrick’s Battalion, 1846– 1848, by Peter F. Stevens, and The Irish Soldiers of Mexico, by Michael Hogan.

Originally published in the September 2014 issue of Military History. To subscribe, click here.