The True Story Of How Irish-American Rebels Fought Against Their Country In The Mexican War

It’s the 1847 Battle of Churubusco during the American war with Mexico. Among the Mexican forces is the Foreign Legion of Patricios, a unit of European volunteers. Many of them are Irish and deserters from the U.S. Army. These men fight with bitter ferocity because they know all too well the grisly fate that awaits them if enemy forces capture them.

We’ll return to the outcome and the decidedly grim aftermath of the Battle of Churubusco later. But first, let’s take a look at the story of the Mexican-American War. We’ll also examine the origins of the Foreign Legion of Patricios or the St. Patrick’s Battalion as it’s perhaps best known in modern times.

The war between America and Mexico began in 1846 and lasted until 1848. Mexico had, in fact, been a sovereign nation since 1821. That’s when the Treaty of Cordoba was signed, freeing the country from the Spanish Empire. It then started out as a monarchy but in 1824 transformed into a republic. From the earliest days of the new nation, though, its northern territories suffered Native American incursions, particularly by the Apache and Comanche peoples.

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The Mexican authorities decided that the best way to stop those raids was to encourage citizens to settle in Texas. This, in turn, would discourage the destructive attacks. The Texans, however, turned out to be just as troublesome as the Native Americans. In the Texas Revolution of 1836, they even declared themselves an independent republic.

Mexico refused to recognize the new republic, so in 1845 the Texans came to an agreement with their U.S. neighbors. Texas would now become the Union’s 28th state, and so it came to pass that the Texans voluntarily became American. The Mexicans were far from happy at this development, although their threats of military action came to nothing.

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Not long after James K. Polk became U.S. president in 1845, he proposed a deal to Mexico. America would buy a substantial tract of land from the Mexican government, roughly the size of California and New Mexico today. The price for the land would be $25 million, with the Rio Grande serving as the border between the two countries. The Mexicans, however, nixed the deal.

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The flashpoint for the simmering dispute was the U.S.’s southern border. The Americans said it was the Rio Grande. The Mexicans claimed it was the River Nueces, further north. Polk now ordered American troops south into the strip of land between the the two rivers. Mexican soldiers then moved north of the Grande.

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It was April 25, 1846, when hostilities first boiled over. A 2,000-strong Mexican cavalry section attacked the 70 men of an American patrol unit in what was known as the Nueces Strip, the land between the Nueces and the Grande. They killed 11 American soldiers and wounded six more during the clash, with the remaining servicemen taken prisoner.

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Shortly after this incident, the U.S. formally declared hostilities against Mexico. Not everyone in the U.S. was happy with this turn of events, however. Some said that American troops had committed an act of aggression by entering the disputed territory of the Nueces Strip which Mexico claimed as its own. Abraham Lincoln, then a member of Congress, was one of the naysayers.

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But the war went ahead regardless. And this conflict brought the Foreign Legion of Patricios that we heard about earlier into the limelight. In fact, this unit is much better known as the Batallón de San Patricio, or St Patrick’s Battalion. This was its original name when it was first formed. St Patrick, of course, is Ireland’s patron saint, which is where most of its soldiers came from.

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One man takes center stage in the story of the St Patrick’s: John Patrick Riley. Riley was born in Ireland in 1817, or thereabouts, in the town of Clifden on the west coast. In Gaelic, his name translated as Seán Ó Raghailligh. But the truth is, we don’t know a great deal about his early life.

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But it seems that Riley joined up with the British Army for a time before moving to Canada, as so many of his countrymen did over the years. From there, it seems he made his way to Michigan. Once he got to the mid-western state, he continued his military career by joining up with the American army.

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Riley signed up for five years of service as a private soldier at Michigan’s Fort Mackinac in September 1845. There, he joined the 5th U.S. Infantry Regiment’s Company K. And for the most part, the company consisted of fellow Irishmen and Germans. And his regimental commander was one General Zachary Taylor, who went on to become the 12th U.S. president in 1849.

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Just a couple of days after Riley joined up, he and his comrades were heading south towards northern Mexico. In March 1846, K Company found itself stationed in Fort Texas, later renamed Fort Brown. This earthwork position was built in the shape of a star under the direction of Captain Joseph K. Mansfield. More importantly, it was north of the Rio Grande, over the river from the Mexican city of Matamoros.

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It was April 12, 1846, when Riley, who had received a promotion to sergeant and was apparently up for an officer’s commission as a lieutenant, asked for permission to attend church. Whether or not he attended the religious service, we do not know. But we do know that this was the end of Riley’s U.S. military career. Why? Because he deserted. And all this happened just a month before the U.S. declared war on Mexico.

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Riley didn’t desert alone, however. In fact, he was with fellow soldier and countryman, Patrick Dalton, whom we’ll meet again later. During 1846, it seems that large numbers of U.S. soldiers defected to Mexico and the St Patrick’s Battalion came into being. Most of the men in the new battalion were Irish, but there were others from the U.S. and Germany. Some sources say the unit had a strength of as many as 200 by the summer of 1846.

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But why would these U.S. soldiers desert to join the army of another country? In fact, the Mexican-American War had a higher rate of desertion than any other conflict involving the U.S. The rate was a little over eight percent, meaning well over 5,000 men left a regular army of just 40,000 involved in the conflict.

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And if you were an Irish Catholic member of the U.S. Army at the time you might well have felt that there was little reason to be loyal to the American flag. Prejudice against Catholics from Ireland, and indeed other countries, was widespread in the 1840s. Many American Protestants viewed Catholics with, at best, suspicion if not downright hostility.

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Many Irish in the U.S. Army may also have believed that the prospect of powerful America taking on its much weaker neighbor in the pursuit of territory was one that left a bad taste in the mouth. And, it seems, at least some Americans very much wanted to spark a war with Mexico.

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The war also involved one of America’s best-known generals, Ulysses S. Grant. As he wrote in his 1885 memoirs, “We were sent to provoke a fight, but it was essential that Mexico should commence it… Once initiated there were but few public men who would have the courage to oppose it.” The general obviously believed that the U.S. was hell-bent on war, and it’s easy to see why some of the Irish found this distaseful.

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And then there was the naked prejudice that the Irish Catholics faced from within the U.S. Army. There were officers in Riley’s own regiment who had strongly held views about them. Some of those men were, in fact, “Nativists.” This was a political movement of the time particularly hostile to Catholics on the grounds that they had allegiance to the Pope instead of America.

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It’s also possible that Riley might have felt personal resentment towards the U.S. military. It seems that the Americans overlooked artilleryman skills he’d learned in the British Army. In any case, Riley and other Catholics, whether from Ireland or elsewhere, felt they had reason enough to cross the Rio Grande and join the Mexicans.

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Mexico, however, played its part in encouraging soldiers to desert from the U.S. Army. In fact, the country had a long tradition of recruiting foreigners to fight for it. For example, when the war with America started, no fewer than 16 of its generals were foreign-born. And during the conflict, the nation’s military made active attempts to recruit U.S. soldiers.

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The country’s authorities did this by distributing handbills that would fall into the hands of American troops. Printed in English, German and French, the leaflets invited U.S. soldiers to join the Mexicans. They promised a warm welcome and better treatment than they got in the American military.

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The propaganda also highlighted that the conflict had, in fact, been forced on Mexico. As a result, they were fighting for their rights and for their religious beliefs, in particular Catholicism. It may well have been that many Irish saw parallels between the Mexican’s situation and the history of their own country. Ireland, after all, had struggled against its British oppressor for generations.

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And Riley emerged as the leader of these disaffected Catholics along with, it’s said, a number of escaped slaves. As commander of the St. Patrick’s Battalion, he led them into battle on many occasions during the conflict. And this unit is said to have offered the toughest opposition the Americans came across.

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Riley has been described as a tall man with dark locks. And he was around 29 or 30 when he joined the Mexicans in 1846. After its formation that same year, his new battalion didn’t have to wait long to see action against its former colleagues. Their first major test came that September during the Battle of Monterrey.

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By the time of the Monterrey battle, the St Patrick’s had become an artillery unit. They were led by the experienced gunnery man Riley who now held the rank of lieutenant. The Mexican forces faced a mix of Texas Rangers, regular army and volunteers led by the artilleryman’s former commander, General Zachary Taylor.

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Riley’s artillery men worked hard to defend the city, repelling three attacks with skillfully directed fire. But the Americans prevailed and the Mexicans, under General Ampudia, surrendered Monterrey. Both sides sustained heavy casualties but the defeated army was allowed to make an orderly retreat. It’s said that Riley had to march by some of his former comrades who hurled choice insults at him.

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Despite this defeat, the numbers joining the St Patrick’s increased to perhaps as many as 700 men. And the Mexican commander, Antonio López de Santa Anna, clearly recognized the military value of the battalion. He now equipped it with Mexico’s heaviest artillery, 16 and 24 pounders. Riley and Dalton then set about exercising their men with the new guns.

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The St Patrick’s next major engagement came on February 23, 1847, at the Battle of Buena Vista. Riley’s men took up a position that gave them a vantage point across the whole battlefield. They succeed in inflicting serious losses on an opposing battery and followed this up with a bayonet charge. Putting the Americans to flight, they now seized two cannon.

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An infuriated General Taylor gave specific orders that Riley and his men be taken out. Soldiers of the U.S. First Dragoons attacked, but the St Patrick’s gave them a bloody nose, forcing them to withdraw. However, the day was not all triumph for the Mexican unit. They later lost up to a third of their men in an artillery battle with the Americans.

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But despite the valiant efforts of Riley and his men, Buena Vista ended in another victory for the Americans, although most of the Mexican forces were allowed to escape. Santa Anna now ordered a reorganization of the St Patrick’s. Given a new name, the Foreign Legion of Patricios, it was now formed of two companies. Colonel Francisco R. Moreno was given overall command while Riley led one of the companies.

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The St Patrick’s next major engagement was the Battle of Churubusco. It was August 20, 1847. After a defeat at the Battle of Padierna the day before, Santa Anna’s forces were in retreat. The battle was a last-ditch attempt to halt the U.S. advance on Mexico City, which was just five miles from the battlefield.

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Santa Anna ordered that the position at Churubusco be held at all costs. The St Patrick’s and other units were positioned at a bridgehead some 500 yards from the fortified Churubusco Convent. Thanks to the battle-hardened St Patrick’s, though, the Mexicans were, for a time, able to repel the strong American assaults.

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After fierce fighting and running short of ammunition, the Mexicans, including the St Patrick’s, were forced to withdraw to the convent fortress. The men of the St Patrick’s are then said to have concentrated on killing American officers in revenge for past slights. After more bitter fighting, though, a Mexican soldier raised a white flag.

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But Patrick Dalton, who had deserted with Riley, angrily ripped the flag down and they fought on. The outcome, though, was inevitable and, after savage hand-to-hand fighting, the St Patrick’s and their Mexican brothers had no choice but to surrender. According to a Mexican battle report, 35 St Patrick’s men lost their lives, 85 got away and enemy forces caught a further 85.

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The U.S. forces now took a terrible revenge. There were two courts-martial in August 1847 which saw 72 men charged with desertion. In the end, a total of 48 men were executed in two separate mass hangings. They hanged because they joined the Mexican Army after war had been declared.

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Those men who deserted and joined the Mexican army before war was declared were not sentenced to death, however. They included Riley, who had deserted four weeks before the declaration. But they hardly got away scot-free. They were each given 50 lashes and had their faces branded with the letter “D” for deserter.

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Victory in this brutal war eventually fell to the Americans in 1848. The Mexicans then had to accept the terms of the Treaty of Guadalupe Hidalgo. This agreement gave the U.S. a huge amount of new territory including California, 50 percent of New Mexico and a large part of Arizona. In addition, the border was now the Rio Grande. Perhaps not many are now familiar with the details of the Mexican-American War. But in Mexico, the heroics of the St Patrick’s are remembered with pride to this day.

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