The question sounds like the start of bad joke, and in fact it is. Posited with this inquiry before I heard the story of John O’Riley, I would likely have responded with an offensive punch line dwelling on the two cultures’ fabled fondness for spirits or insouciant approach to life. Yet, as Saint Patrick’s Day approaches, I find myself armed with something new to say.

During the 1840s, thousands of immigrants, mostly the Irish-Catholic diaspora who, driven from the isle by the Great Potato Famine, came to the United States. Many were lured by the promise of a noble career, a decent salary, and the opportunity to escape heavy Anti-Irish sentiments. However, donning a uniform emblazoned by the U.S. flag did not stifle prejudice against the Irish.

By 1846 the United States was intent on invading Mexico. The ostensible reason was to collect on past-due loans and indemnities. The real reason was that this country sought to gain control of valuable Mexican territories which at that time included: the ports of San Francisco and San Diego, the trade route through New Mexico and mineral-rich Nevada.

Many Irish empathized with Mexico from the onset of the Mexican-American War. Like Ireland, Mexico was a Catholic country that was being invaded by a Protestant power. Most Irish Immigrants knew little about this country’s heritage and culture. What they quickly learned was that earlier settlers were not particularly fond of Irish-Catholics. For more than a decade, members of the Know Nothing political movement plundered and torched Catholic convents, churches and schools and murdered at minimum two dozen Catholics with impunity.

Fueled by a palpable sense of animosity and an opportunity to aid a country all too similar to their own, many Irish conscripts deserted their U.S. military posts and joined the ranks of the Mexican army.

The San Patricio Battalion’s role in the U.S.-Mexico War began with U.S. immigrant John O’Riley, born in Clifden, County Galway, enlisting in the Mexican army in March of 1846. Quickly, O’Riley persuaded 48 fellow Irishmen to fight alongside him for Mexico. Enlistments soon swelled to more than 200. Under their distinct green banner, the San Patricios participated in all of the war’s major battles. It was cited for bravery by then-Mexican President General López de Santa Anna. During the battle of Churubusco, the Patricios fought long after they had exhausted their ammunition.

    When their Mexican comrades raised the white flag suggesting surrender, they tore it down, preferring to fight with their bayonets and bare hands. When the brutal battle reached its conclusion, 85 Patricios had been captured. Of those, 72 were tried by a court martial. In accordance with the court’s order, 50 soldiers who joined O’Riley’s ranks after the U.S. had officially declared war were hanged and the 16, which included O’Riley, who took up arms with Mexico before the official start of the war were  flogged and branded on the cheek with a “D” for desertion.   

To this day, O’Riley and the Patricios are regarded as heroes in Mexico and Ireland. Mexico celebrates the Irish soldiers on two separate days every year; Sept. 12 commemorates the execution of the Patricios, and March 17, Saint Patrick’s Day.  In Ireland, a bronze sculpture of O’Riley was erected in his birthplace of Clifden, County Galway.

So, this Saint Patrick’s Day if you find yourself in a pub with stein full of green beer and someone asks what a Mexican has in common with an Irishmen, tell him the willingness to fight for noble ideas and just causes, and indulge them with the tale of the San Patricio Battalion. Remember, on Saint Paddy’s day, we’re all just a little bit Irish, just as the Irish are a little bit Mexican.

(Adrian Rocha is a reporter with Hispanic Link News Service in Washington, D,C. Email him at [email protected].)