Saint Patrick ' s Battalion The Saint Patrick ' s Battalion ( ) , formed and led by Jon Riley , was a unit of 175 to several hundred immigrants ( accounts vary ) and expatriate s of European descent who fought as part of the Mexican Army against the United States in the Mexican - American War of 1846 to 1848 . Most of the battalion ' s members had deserted or defected from the U . S . Army . Made up primarily of ethnic Irish and German Catholic immigrants , the battalion included Canadians , English , French , Italians , Poles , Scots , Spaniards , Swiss , and native Mexicans , most of whom were Roman Catholics . Disenfranchised Americans were in the ranks , including escaped slaves from the American South . The Mexican government offered incentives to foreigners who would enlist in its army : granting them citizenship , paying higher wages than the U . S . Army and the offer of generous land grants . Only a few members of the Saint Patrick ' s Battalion were actual U . S . citizens . Members of the Battalion are known to have deserted from U . S . Army regiments including : the 1st Artillery , the 2nd Artillery , the 3rd Artillery , the 4th Artillery , the 2nd Dragoons , the 2nd Infantry , the 3rd Infantry , the 4th Infantry , the 5th Infantry , the 6th Infantry , the 7th Infantry and the 8th Infantry . The Battalion served as an artillery unit for much of the war . Despite later being formally designated as infantry , it still retained artillery pieces throughout the conflict . In many ways , the battalion acted as the sole Mexican counter - balance to U . S . horse artillery . Historical perspective . For Americans of the generation that fought the Mexican - American War , the " San Patricios " were considered traitors . For Mexicans of that generation , and generations to come , the " San Patricios " were heroes who came to the aid of fellow Catholics in need . The great majority of these men were recent immigrants who had arrived at northeastern U . S . ports , part of the Irish diaspora then escaping the Great Irish Famine and extremely poor economic conditions in Ireland , part of the United Kingdom of Great Britain and Ireland at the time . The U . S . Army often recruited Irishmen and other immigrants into military service shortly or sometimes immediately on arrival , with promises of salaries and land after the war . Numerous theories have been proposed as to their motives for desertion , including cultural alienation , mistreatment of immigrant soldiers by nativist soldiers and senior officers , their not being allowed to attend Sunday Mass or to practice their religion freely , the incentive of higher wages and land grants starting at offered by Mexico , and their witnessing poor conduct of U . S . troops following battle victories . Some historians believed a primary motivation was shared religion with the Mexicans and sympathy for the Mexican cause , likely based on similarities between the situations in Mexico and Ireland . This hypothesis is based on evidence of the number of Irish Catholics in the Battalion , the letters of Jon Riley , and the field entries of senior officers . Another hypothesis is that the members of the Saint Patrick ' s Battalion had been unhappy with their treatment in the U . S . Army . Another theory some historians hold is that the soldiers were attracted by the valuable incentives offered by the Mexican government : higher wages and generous land grants . For poor people coming from famine conditions , economics was often an important incentive . Mexican author José Raúl Conseco noted that many Irish lived in northern Texas , and were forced to move south due to regional insecurity . Early in the war they helped Gen . Taylor attack the fort and supply depot in St . Isabel , now the city of Port Isabel , Texas . Irish expatriates had a long tradition of serving in military forces of Catholic countries , for instance , serving with Spain and later France in groups of young men who had left Ireland during what would become known as the Flight of the Wild Geese in the 17th century . In addition , many Irish fought as soldiers in South American wars of independence . Flag . There are conflicting accounts of the design of the flag of the Saint Patrick ' s Battalion . No flags or depictions of them are known to have survived to the present day . The only version of the flag known to have survived the war was subsequently lost or stolen from the chapel at West Point . Jon Riley , who left an account of the battalion , noted the flag in a letter : According to an American journalist covering the war with Mexico : Two other eye - witness accounts of the flag exist , both from American soldiers . The first describes it as : The second notes only : A radically different version of the flag was described in this Mexican source : Whatever the case , in 1997 a reproduction military flag was created by the Clifden and Connemara Heritage Group . Another was created the following year for the MGM film " One Man ' s Hero " . The film was a romanticised version of the San Patricios ' history . A third version embodying the description of the San Luis Potosí flag was made for the Irish Society of Chicago , which hung it in Chicago ' s Union League Club . Some theories suggest that the Saint Patrick ' s Battalion might have used different banners ( as an artillery unit , an infantry company and as a reconstructed unit ) . Service as a military unit . Formation and early engagements . Present in the Mexican Army for the battles of Palo Alto and Resaca de la Palma were the " Legión de Extranjeros " ( Legion of Foreigners ) ; the men who would later make up the core of the Saint Patrick ' s battalion . Meanwhile , Riley and " a company of 48 Irishmen " manned Mexican artillery at the Siege of Fort Texas , which took place concurrently to the two other battles . The Saint Patrick ' s Battalion first fought as a recognised Mexican unit in the Battle of Monterrey on 21 September 1846 , as an artillery battery . Popularly they were called " Los Colorados " by the Mexicans because of their ruddy , sun - burnt complexions and red hair color . They were commanded by Jon Riley , an Irish artilleryman and veteran non - commissioned officer of the British Army , who possibly arrived in Canada in 1843 whilst serving in the British Army ( the assertion that he served as a Sergeant in the 66th ( Berkshire ) Regiment of Foot , is known to be a fabrication ) going on to join the U . S . Army in Michigan in September 1845 . He deserted in Matamoros in April 1846 . Upon meeting Mexican forces he was initially given the Officers rank of Lieutenant by General Pedro de Ampudia . At the battle of Monterrey the San Patricios proved their artillery skills by causing the deaths of many American soldiers , and they are credited with defeating two to three separate assaults into the heart of the city . Among their targets were companies led by such officers as Braxton Bragg , many of whose soldiers would end up in their own ranks later in the war . Their tenacity , however , did not affect the Mexican commanders ' decision to capitulate and abandon the position . Following the engagement at Monterrey , the San Patricios grew in number , by some estimates reaching an enlistment of over 700 men . Forces re - assembled at San Luis Potosí and they had their distinct green silk flag embroidered there . Buena Vista . They then marched northward after joining a larger force commanded by Antonio López de Santa Anna sent from Mexico City , the " liberating army of the North " . At the Battle of Buena Vista ( known as the battle of Angostura in Mexico ) in Coahuila on 23 February , the Patricios became engaged with U . S . forces . They were assigned the three heaviest — 18 and 24 pound — cannons the Mexican army possessed , which were positioned on high ground over - looking the battle field . They were later described as " a strong Mexican battery . . . moved . . . by dint of extraordinary exertions . . . [ that ] commanded the entire plateau " . They started the battle supporting Mexican infantry by firing on U . S . lines as the Mexicans advanced on them , then later decimating an artillery battery directly opposite them on the battlefield ( Washington ’ s 4th Artillery , D Battery ) . A small number of San Patricios were dispatched with a division commanded by Manuel Lombardini with the express purpose of capturing the 4th ' s cannons once the crews had been dealt with . As the division got close enough they charged the artillery battery , bayoneting whoever remained and rout ing the rest , leaving the attached San Patricios free to haul away two six - pound cannons . These cannons would later be used by Mexican forces at the Battle of Contreras . In frustration U . S . Commander Zachary Taylor , referring to the Saint Patrick ' s Battalion , ordered a squadron of the 1st Dragoons to " take that damned battery " . In this task they failed , and , badly bloodied , were forced to retreat . At about 1 p . m . the San Patricios covered a Mexican retreat as a disordered mass of infantry 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 them . Several Irishmen were awarded the War Cross by the Mexican government for their conduct in that battle , and many received field promotions . Re - organization and final battles . Despite their excellent performance in a number of engagements as artillery , the much - reduced San Patricios were ordered to muster a larger infantry battalion in mid - 1847 by personal order of Santa Anna . It was re - named the " The Foreign Legion of Patricios " and consisted of volunteers from many European countries , commanded by Col . Francisco R . Moreno , with Riley in charge of 1st company and Santiago O ' Leary heading up the second . As an infantry unit , the San Patricios continued to serve with distinction . Knowing that they were likely to face the death penalty if captured , the San Patricios are known to have threatened wavering Mexican troops with death by " friendly fire " at the Battle of Cerro Gordo if they retreated . When the San Patricios were too - heavily engaged to carry out their threat , the Mexican troops broke and ran , leaving the San Patricios as they fought U . S . troops in hand - to - hand combat . The Battle of Churubusco ( 20 August 1847 ) took place about four months after the defeat at Cerro Gordo . Gen . Santa Anna gave a verbal order to " preserve the point at all risk " . The San Patricio Companies initially met the attackers outside the walls of the convent at a tête - de - pont , which was about from a fortified convent . A battery of three to five heavy cannons were used from this position to hold off the American advance along with support from " Los Independencia Batallón " and " Los Bravos Batallón " . Several U . S . charges towards the bridgehead were thrown off , with the San Patricio companies serving as an example to the supporting battalions . Unlike the San Patricios , most of whom were veterans ( many having served in the armies of the United Kingdom and assorted German states ) , the supporting Mexican battalions were simply militia ( the term ' National Guard ' is also used ) who had been untested by battle . A lack of ammunition led the Mexican soldiers in the trenches between the bridgehead and the convent to disband ; without ammunition , they had no way to fight back . Santa Anna had ordered half of these soldiers to a different part of the battlefield . When the requested ammunition wagon finally arrived , the 9 ½ drachm cartridges were compatible with none but the San Patricio Companies " Brown Bess " muskets , and they made up only a fraction of the defending forces . Further hampering Mexican efforts , a stray spark from an artillery piece firing grape shot at the on - coming U . S . troops caused the just - arrived ammunition to explode and set fire to several men , including Captain O ' Leary and Gen . l Anaya . A withdrawal behind the walls of the " convento de Churubusco " was called when the threat of being outflanked proved too great . The San Patricios used this battle as a chance to settle old scores with U . S . troops . " The large number of officers killed in the affair was . . . ascribed to them , as for the gratification of their revenge they aimed at no other objects during the engagement " . Though hopelessly outnumbered and underequipped , the defenders repelled the attacking U . S . forces with heavy losses until their ammunition ran out and a Mexican officer raised the white flag of surrender . Officer Patrick Dalton of the San Patricios tore the white flag down , prompting Gen . Pedro Anaya to order his men to fight on , with their bare hands if necessary . American Private Ballentine reported that when the Mexicans attempted to raise the white flag two more times , members of the San Patricios shot and killed them . After brutal close - quarters fighting with bayonet s and sabers through the halls and rooms inside the convent , U . S . Army Captain James M . Smith suggested a surrender after raising his white handkerchief . Following the U . S . victory , the Americans " ventilat [ ed ] their vocabulary of Saxon expletives , not very " courteously , " on Riley and his beautiful disciples of St . Patrick . " Gen . Anaya stated in his written battle report that 35 San Patricios were killed , 85 taken prisoner ( including a wounded Jon Riley , Captain O ' Leary and Anaya ) . About 85 escaped with retreating Mexican forces . The survivors were reformed before the Battle of Mexico City some two weeks later and were stationed at Querétaro . New units were made up of the free survivors of the battle of Churubusco and a roughly equal number of fresh deserters from the U . S . Army . Following the war , the battalion never regained its former numbers ; it was officially mustered out of Mexican military service in 1848 . Some members were alleged to have been involved in an abortive military coup ; historians have said the group was disbanded because of Mexican budget cuts . Aftermath . Trials . The San Patricios captured by the U . S . Army were treated and punished as traitors for desertion in time of war . In addition , they had been responsible for some of the toughest fighting ( and the heaviest casualties ) that the U . S . Army had faced . Seventy - two men were immediately charged with desertion by the Army . Two separate courts - martial were held , one at Tacubaya on 23 August , and another at San Ángel on 26 August . At neither of these trials were the men represented by lawyers nor were transcripts made of the proceedings . This lack of formal legal advice could account for the fact that several of the men claimed that drunkenness had led them to desert ( a common defense in military trials at the time that sometimes led to lighter sentences ) , and others described how they were forced to join the Mexican Army in some form or another . The majority of the San Patricios either offered no defense or their defenses were not recorded . In any case , military law required death as the punishment for the crime of desertion during a time of war . Sentences . One soldier who claimed he was forced to fight by the Mexicans after he was captured by them , and who subsequently refused to do so , was sentenced to death by firing squad instead of hanging , along with another who was found not to have officially joined the Mexican Army . Most of the convicted San Patricios were sentenced to death by hanging : 30 from the Tacubaya trial and 18 from San Ángel . The rationale was that they had entered Mexican military service following the declaration of war . Execution by hanging was in violation of the contemporary Articles of War , which stipulated that the penalty for desertion and / or defecting to the enemy during a time of war was death by firing squad , regardless of the circumstances . Hanging was reserved only for spies ( without uniform ) and for “ atrocities against civilians ” , neither of which activities were among the charges brought against any members of the Saint Patricio ' s Battalion . Although more than 9 , 000 U . S . soldiers deserted the army during the Mexican - American War , only the San Patricios ( who unlike almost all other deserters had also fought against the United States ) were punished by hanging . Those soldiers who had left military service before the official declaration of war on Mexico ( Riley among them ) were sentenced to : Executions . En masse hangings for treason took place on 10 September 1847 , at San Ángel ( where 16 were hanged ) and the village of Mixcoac ( where 4 were hanged ) , and 13 September at Chapultepec . At the San Ángel hangings all prisoners were executed without incident except for Patrick Dalton , who , as an American captain described , was " literally choked to death " . Dalton had previously voiced concerns regarding his treatment . By order of Gen . Winfield Scott , 30 San Patricios were to be executed at Chapultepec in full view of the two armies who had fought there , at the precise moment that the flag of the U . S . replaced the flag of Mexico atop the citadel . This order was carried out by Col . William Harney . While overseeing the hangings , Harney ordered Francis O ' Connor hanged even though he had had both legs amputated the previous day . When the army surgeon informed the colonel that the absent soldier had lost both his legs in battle , Harney replied : The U . S . flag appeared on the flagpole at 9 . 30 a . m . The Mexican flag had been taken , according to legend , by cadet Juan Escutia to his death after leaping with it from Chapultepec Castle to deny the Americans the honor of capturing it . In a final act of defiance , the men about to be hanged cheered the Mexican flag , as one onlooker remarked ; " Hands tied , feet tied , their voices still free " . At Harney ' s signal , the carts holding the tied and noosed men pulled away . Harney was subsequently promoted to brigadier general , a post which he held while the U . S . Army occupied Mexico City . The Mexican government described the hangings as “ a cruel death or horrible torments , improper in a civilized age , and [ ironic ] for a people who aspire to the title of illustrious and humane ” , and by a writer covering the war as " a refinement of cruelty and . . . fiendish " . Legacy . Those who survived the war generally disappeared from history . A handful are on record as having made use of the land claims promised them by the Mexican government . The men have continued to be honored and revered as heroes in Mexico . The " Batallón de San Patricio " is memorialised on two separate days ; 12 September , the generally - accepted anniversary of the executions of those convicted by the U . S . Army of desertion at time of war , and 17 March , Saint Patrick ' s Day . Numerous schools , churches and other landmarks in Mexico take their name from the battalion , including : In the U . S . the memory of the battalion has been different . The U . S . Army denied the existence of the Saint Patrick ' s battalion as a cover - up and attempt to discourage other deserters . In 1915 an inquiry was initiated by U . S . congressmen William Henry Coleman and Frank L . Greene . This resulted in the U . S . Army ' s admitting its denial of the matter . The U . S . Congress ordered the army to turn over its records on the battalion to the National Archives . In the past most Irish Americans distanced themselves from the battalion , as they did not want to be associated with deserters or thought to be disloyal . In 1997 , President Ernesto Zedillo commemorated the 150th anniversary of the execution of the San Patricios at a ceremony in Mexico City ' s San Jacinto Plaza . This is where the U . S . Army conducted the first 16 hangings after the men were convicted of desertion at court martial . Ireland and Mexico jointly issued commemorative postage stamps to mark the anniversary . In 2004 , at an official ceremony attended by numerous international dignitaries including directors Lance and Jason Hool , as well as several actors from the film " One Man ' s Hero " ( 1999 ) , the Mexican government gave a commemorative statue to the Irish government in perpetual thanks for the bravery , honor and sacrifice of the Saint Patrick ' s Battalion . The statue was erected in Clifden , Connemara , Ireland , where leader Jon Riley was born . The battalion has inspired numerous responses : it is the name of a soccer team club Deportivo Chivas USA ' s supporters association , was evoked in a Saint Patrick ' s Day message from Subcomandante Marcos of the Zapatista Army of National Liberation , and has been remembered as a symbol of international solidarity with Mexico . In honor of Jon Riley , on 12 September the town of Clifden flies the Mexican flag .