On Aug. 18, 1847, Mexican General Gabriel Valencia — in charge of 7,000 armed troops supported by 23 cannons — defied a direct order by Commanding General Antonio López de Santa Anna to pull back. Protected by what he considered impenetrable mountains and a vast volcanic lava field, Valencia felt confident he could stop the enemy there. But the Americans found paths through the fissures of calcified lava.
The American army approached the Churubusco Monastery knowing that victory there would lead to the invasion of Mexico City and the war’s end.
At dawn on Aug. 19, U.S. troops rushed into the Mexican camp of sleepy, hungover soldiers and cut them down by the hundreds. Panicked, Valencia’s army crumbled in 17 minutes. Santa Anna watched the mayhem through his field glass from 2,000 yards away, but declined to bring his 12,000 troops into the fight to crush the vastly outnumbered Americans, a decision that ultimately cost him the war.
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The American army approached the Churubusco Monastery knowing that victory there would lead to the invasion of Mexico City and the war’s end. American soldiers ran toward the formidable defenses manned by St. Patrick’s Battalion and Mexican regulars. Leader John Patrick Riley ran the battalion’s distinctive green flag up behind his gun battery in plain view of the Americans.
When the leading troops of the American infantry were 60 yards away, Riley yelled “Fire!” The fusillade tore into the U.S. soldiers, killing and wounding hundreds and sending the rest scrambling into nearby corn fields for protection. Subsequent charges withered in the hail of bullets. For hours the Americans were pinned down and at the mercy of musket and cannon fire from the convent. Riley and his men directed their artillery with the accuracy of trained snipers.
As American soldiers slowly crawled forward in mud among the corn stalks, they were incensed by the deserters and the hated green flag of the St. Patrick’s Battalion. For Riley and his men, it symbolized Irish resistance to the religious discrimination and physical abuse systemic in the U.S. Army at that time, as well as their sympathy for Catholic Mexicans protecting their homeland against invaders.
When the Churubusco defenders ran out of ammunition, U.S. soldiers stormed the complex. Riley and 84 of his men were taken into custody. Shackled in chains, the survivors were dragged into a courtyard piled high with the dead and wounded from both sides. American soldiers cursed and spat at Riley and the other defectors — only strict discipline kept the emotional troops from killing the deserters. One officer fumed: “These wretches served the guns — the use of which they had been taught in our own service — and with fatal effect, upon the persons of their former comrades.”
The U.S. suffered 1,031 dead or wounded on Aug. 20 in the bloodiest day of fighting in a war that claimed a total of 1,722 Americans. The fierce resistance by the San Patricios and their mastery of heavy guns took out nearly 12 percent of Gen. Winfield Scott’s 9,000 troops. On the Mexican side, more than 6,000 of Gen. Santa Anna’s soldiers were killed or wounded.
Seventy-two renegades were charged with desertion of duty and brought to trial. Others were released due to assorted mitigating circumstances. Well aware of a policy that allowed drunken AWOL soldiers back into the ranks, 32 Irishmen pleaded not guilty due to intoxication. They claimed that they were on drinking sprees when captured by Mexicans and forced to bear arms against the Americans. At the time, the Articles of War considered drunkenness a valid legal defense to the specific crime of desertion.
The officers conducting the court martial ignored these arguments and all of the defendants were sentenced to death by hanging, except two that were to be shot by firing squad. The court’s verdicts were sent to Gen. Scott for final approval, modification or dismissal. Scott reprieved the death warrants for some of the men, including San Patricio leader Maj. Riley. Riley and these other U.S. soldiers had deserted before the 1846 declaration of war by Congress and Articles of War provisions stipulated that these men could not be given the death penalty.
Instead they were punished with 50 lashes (the maximum allowed), branded by hot iron with the letter “D” for deserter on their hip — 1 inch in length and with indelible ink. Scott ordered Riley and some of the other defectors to be branded on their face, a particularly sadistic act that violated the provisions in the Articles of War. In fact, for Riley, when the letter was mistakenly burned into his cheek upside down, the soldier wielding the hot iron was ordered to do it again correctly. And during Riley’s lashing with knotted rawhide, the officer in charge pretended to lose count and the leader of the Irish battalion was whipped 59 times.
For Mexican observers, the public spectacle was shocking and appalling. Citizens and clergy were aghast at the barbaric torture that the Americans carried out against their own people. The total of 50 men hanged during those 72 hours is still the largest mass execution in U.S. history.
The punishments, cruel, unusual and excessive even by the standards of the 1840s American military, and the way they were carried out, were emblematic of the contempt and revulsion against Irish-Catholic immigrants by officers in the U.S. Army specifically, and by America’s Protestant-centric culture in general at that time.
After the war, all military prisoners were released. John Riley and the other freed San Patricios were destitute. The Mexican Minster of War sent Riley and his men money and invited them to re-enlist in a newly reconstituted St. Patrick’s Battalion that the Mexican Army needed to help provide order in the country’s post-war chaos.
In U. S. military history, the St. Patrick’s Battalion is vilified as traitorous deserters who inflicted heavy casualties against the American army. But in Mexico the battalion is revered for brave actions against the Yankee invaders. The old Monastery of Churubusco in Mexico City now houses the National Museum of the Interventions. The museum recounts the history of unwanted incursions into Mexico by foreign forces, such as the Spanish, American and French.
In the town of San Angel, there is a large monument that lists the names of 71 soldiers who switched sides to fight for Mexico; the majority of surnames were Irish (48) and German (13). At the top of the marble edifice is the Celtic cross of Ireland with the inscription: “In Memory of the Heroic Battalion of Saint Patrick, Martyrs Who Gave Their Lives for the Mexican Cause during the Unjust North American Invasion of 1847.”