Biography of John Riley

John Riley
Photo by Christopher Minster

John Riley (Circa 1805-1850) was an Irish soldier who deserted the American army just before the outbreak of the Mexican-American War. He joined the Mexican army and founded the St. Patrick's Battalion, a force made up of fellow deserters, primarily Irish and German Catholics. Riley and the others deserted because treatment of foreigners in the US army was very harsh and because they felt that their allegiance was more with Catholic Mexico than Protestant USA. Riley fought with distinction for the Mexican army and survived the war only to die in obscurity.

Early Life and Military Career

Riley was born in County Galway, Ireland sometime between 1805 and 1818. Ireland was a very poor country at the time and was hit hard even before the great famines began around 1845. Like many Irish, Riley made his way to Canada, where he likely served in a British army regiment. Moving to Michigan, he enlisted in the US army before the Mexican-American War. When sent to Texas, Riley deserted to Mexico on April 12, 1846, before the war officially broke out. Like other deserters, he was welcomed and invited to serve in the Legion of Foreigners which saw action in the bombardment of Fort Texas and the Battle of Resaca de la Palma.

The Saint Patrick's Battalion

By April of 1846, Riley had been promoted to Lieutenant and had organized a unit comprised of 48 Irishmen who joined the Mexican army. More and more deserters came over from the American side and by August of 1846, he had over 200 men in his battalion. The unit was named el Batallón de San Patricio, or the St. Patrick's Battalion, in honor of Ireland's patron saint. They marched under a green banner with an image of St. Patrick on one side and a harp and emblem of Mexico on the other. As many of them were skilled artillerymen, they were assigned as an elite artillery regiment.

Why Did the San Patricios Defect?

During the Mexican-American War, thousands of men deserted on both sides: conditions were harsh and more men died of illness and exposure than in combat. Life in the US army was particularly tough on Irish Catholics: they were seen as lazy, ignorant and foolish. They were given dirty and dangerous jobs and promotions were virtually non-existent. Those who joined the enemy side most likely did so because of the promises of land and money and out of loyalty to Catholicism: Mexico, like Ireland, is a Catholic nation. The St. Patrick’s Battalion was comprised of foreigners, mainly Irish Catholics. There were some German Catholics as well, and some foreigners who lived in Mexico before the war.

The Saint Patricks in Action in Northern Mexico

The St. Patrick's Battalion saw limited action at the siege of Monterrey, as they were stationed in a massive fortress that American General Zachary Taylor decided to avoid entirely. At the Battle of Buena Vista, however, they played a major role. They were stationed alongside the main road on a plateau where the main Mexican assault took place. They won an artillery duel with an American unit and even made off with some American cannons. When Mexican defeat was imminent, they helped cover the retreat. Several San Patricios won a Cross of Honor medal for valor during the battle, including Riley, who was also promoted to captain.

The San Patricios in Mexico City

After the Americans opened another front, the San Patricios accompanied Mexican General Santa Anna to the east of Mexico City. They saw action at the Battle of Cerro Gordo, although their role in that battle has been largely lost to history. It was at the Battle of Chapultepec that ​they made a name for themselves. As the Americans attacked Mexico City, the Battalion was stationed at one end of a key bridge and in a nearby convent. They held the bridge and convent for hours against superior troops and weapons. When Mexicans in the convent tried to surrender, the San Patricios tore down the white flag three times. They were eventually overwhelmed once they ran out of ammunition. Most of the San Patricios were killed or captured at the Battle of Churubusco, ending its effective life as a unit, although it would re-form after the war with the survivors and last for about another year.

Capture and Punishment

Riley was among the 85 San Patricios captured during the battle. They were court-martialed and most of them were found guilty of desertion. Between September 10 and 13, 1847, fifty of them would be hanged in punishment for their defection to the other side. Riley, although he was the highest-profile among them, was not hanged: he had defected before the war had officially been declared, and such defection in peacetime was by definition a far less serious offense.

Still, Riley, by then a major and highest ranking foreign officer of the San Patricios (the Battalion had Mexican commanding officers), was punished harshly. His head was shaved, he was given fifty lashes (witnesses say the count was botched and that Riley actually received 59), and he was branded with a D (for deserter) on his cheek. When the brand was at first put on upside down, he was re-branded on the other cheek. After that, he was thrown in a dungeon for the duration of the war, which lasted several more months. In spite of this harsh punishment, there were those in the American army who felt he should have been hanged with the others.

After the war, Riley and the others were released and re-formed the St. Patrick's Battalion. The unit soon became embroiled in the constant infighting among Mexican officials and Riley was briefly jailed for suspicion of participation in an uprising, but he was freed. Records indicating that a "Juan Riley" died on August 31, 1850, were once believed to refer to him, but new evidence indicates that this is not the case. Efforts are ongoing to determine Riley's true fate: Dr. Michael Hogan (who has written the definitive texts about the San Patricios) writes "The search for the burial place of the true John Riley, Mexican major, a decorated hero, and leader of the Irish battalion, must continue."

The Legacy 

To Americans, Riley is a deserter and a traitor: the lowest of the low. To Mexicans, however, Riley is a great hero: a skilled soldier who followed his conscience and joined the enemy because he thought it was the right thing to do. The St. Patrick's Battalion has a place of great honor in Mexican history: there are streets named for it, memorial plaques where they fought, postage stamps, etc. Riley is the name most commonly associated with the Battalion, and he has, therefore, gained extra heroic status for Mexicans, who have erected a statue of him in his birthplace of Clifden, Ireland. The Irish have returned the favor, and there is a bust of Riley now in the San Angel Plaza, courtesy of Ireland.

Americans of Irish descent, who once disowned Riley and the Battalion, have warmed to them in recent years: perhaps in part due to a couple of good books that have come out recently. Also, there was a major Hollywood production in 1999 entitled "One Man's Hero" based (very loosely) on the life of Riley and the Battalion.


Hogan, Michael. "The Irish Soldiers of Mexico." Paperback, CreateSpace Independent Publishing Platform, May 25, 2011.

Wheelan, Joseph. Invading Mexico: America's Continental Dream and the Mexican War, 1846-1848. New York: Carroll and Graf, 2007.

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Your Citation
Minster, Christopher. "Biography of John Riley." ThoughtCo, Aug. 26, 2020, Minster, Christopher. (2020, August 26). Biography of John Riley. Retrieved from Minster, Christopher. "Biography of John Riley." ThoughtCo. (accessed January 28, 2023).