The San Patricio Battalion

The Mexican-American War (1846-1848) marked the first U.S. armed conflict chiefly fought on foreign soil. It pitted a politically divided and militarily unprepared Mexico against the expansionist-minded administration of U.S. President James K. Polk, who believed the United States had a "manifest destiny" to spread across the continent to the Pacific Ocean. A border skirmish along the Rio Grande incited the fighting, followed by a series of U.S. victories. When the dust cleared, Mexico had lost about one-third of its territory, including nearly all of present-day California, Utah, Nevada, Arizona and New Mexico.

The San Patricio Battalion (St. Patrick's Battalion) was also known as the Irish Volunteers or Los Colorados because of the disproportionate number of red-headed soldiers. San Patricio Guards; San Patricio Company; Foreign Legion; Legion of Strangers and other designations, were names also applied to these immigrants to America (some of them US Army deserters), who fought on the Mexican side in the War of 1846-1848.

The Saint Patrick's Battalion first fought as a Mexican artillery battery at the Battle of Monterrey on September 21, 1846. They were commanded by John Patrick Riley. He was an Irish artilleryman and veteran non-commissioned officer of the British Army, who possibly arrived in Canada in 1843 while still serving in the British army. He later enlisted in the US Army prior to fighting for Mexico. Upon joining the Mexican forces, he was initially given the officer rank of Lieutenant by General Pedro de Ampudia. Eventually he would be promoted to Brevet Major.


John Riley Bust
in the Plaza San Jacinto, San Angel, Mexico City


Following the engagement at Monterrey, the San Patricios grew in number, by some estimates reaching a compliment of more than 700 men. Their forces re-assembled at San Luis Potosi where they had their distinct green silk flag embroidered.

At the Battle of Buena Vista (also known as the battle of Angostura in Mexico) on February 22- 23, 1847, the San Patricio engaged with U.S. forces. They were assigned the three heaviest 18 and 24 pound cannons, which the Mexican army possessed and which were positioned on high ground overlooking the battlefield. The San Patricio’s accuracy decimated the Washington 4th Artillery, D Battery directly opposite them on the battlefield.


San Patricio Battalion Members


Escudo de San Patricio & Commemorative Gold Coin (1960)


The San Patricios eventually covered a Mexican retreat as a disorganized mass of infantrymen sought refuge during a lull in the fighting. The San Patricios rode out the day in a costly artillery duel with several American batteries, which killed and injured roughly one third of the San Patricio forces. General Francisco Mejia's Battle Report for Buena Vista described the San Patricios as "worthy of the most consummate praise because the men fought with daring and bravery." Research states that several Irishmen were awarded the War Cross* by the Mexican government for their conduct during the battle. Many fighters of the San Patricio also received field promotions.

The Battle of Churubusco was the greatest effort and final battle for the San Patricio. The San Patricio were divided and sent to defend one of the approaches to Mexico City. Some were stationed at defensive works at one end of a causeway into Mexico City; others were in a fortified convent. When the Americans attacked on August 20, 1847, the San Patricio fought like demons. In the convent, Mexican soldiers three times tried to raise a white flag and each time the San Patricio ripped it down. They only surrendered when they ran out of ammunition. Most of the San Patricio were either killed or captured in this battle. Some however, were able to escape into Mexico City, but not enough to form a cohesive army unit. John Riley was among those captured. Less than a month later, Mexico City was taken by the Americans and the war was over.

Many of the captured San Patricios were treated and punished as traitors for desertion in time of war by the U.S. Army. Seventy-two men were immediately charged with desertion by the Army. Fifty members of the San Patricio Battalion were officially executed by the U.S. Army. John Riley escaped execution, since he deserted prior to the commencement of the hostilities. Instead, he was branded on the cheek with the letter "D" for deserter. Commissioned as a permanent Major, Riley continued to serve until August 1850 when he was honorably discharged from the Mexican Army with medals for heroism. What was taken for a death certificate, states a Juan Riley was buried in Veracruz the same month as Riley's discharge. This record has been called into doubt due to several discrepancies and his ultimate whereabouts remain unknown.

Traitors and deserters in the eyes of the United States, the San Patricio remain to this day heroes to the Mexicans.


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