Harney Re-Examined Part IV: Harney and the Hanging of the San Patricio Brigade

This painting illustrates the hanging of the San Patricio Brigade. Harney is presumably the man on horseback in the foreground

On the morning of September 13, 1847, William Harney watched as American forces stormed Chapultepec Castle, the last major citadel protecting Mexico City from the invading US Army. At 9:30 A.M. the US flag rose above the Mexican fortress, signaling that his side had won the battle and that it was time to execute his captives. Harney ordered his mule carts forward, tightening the nooses on 30 men. This was the last of 3 mass executions that General Winfield Scott had ordered against the San Patricio (Saint Patrick) Brigade, a group of mostly Irish immigrants who fought on the side of Mexico in the Mexican-American War.

The Mexican-American War divided the American people. Some Northerners, such as then-Congressman Abraham Lincoln, saw the US invasion of Mexico as “‘from beginning to end, the sheerest deception,” because it was unprovoked and unjustified. Lincoln argued (and most historians agree) that President Polk sent the US Army into disputed territory hoping to provoke Mexican soldiers to protect their homeland. With American troops under fire, the congress wrote Polk a blank check to fund the invasion of Mexico that he had long desired.
Many Americans considered Polk’s actions as part of a broader “Slave Power Conspiracy.” Though most Americans lived in free states and many opposed slavery, the federal government was overwhelmingly dominated by slaveholders. That led to laws and policies that favored slaveholders and slave states. From this viewpoint, the war with Mexico was a scheme to conquer parts of Mexico and make them into slave states. Some members of the San Patricio Brigade had already seen this happen in Texas, which had been seized from Mexico by slaveholding Americans a decade earlier.

The San Patricio Brigade was made up mostly of Irish immigrants who objected to the war. Many were American soldiers who resented the way abusive officers like Harney treated enlisted men. Some were traumatized survivors of the Irish Potato Famine.They had watched their friends and loved ones starve because of British imperial policies that favored Protestant settlers over the Irish Catholic majority. Even in the US Army, many of these immigrants encountered anti-Catholic bigotry and brutal discipline that left them feeling disenchanted. For men who grew up in an occupied country, the US invasion of Mexico reminded them of the British dominance of Ireland.

Not all members of the San Patricio Brigade were Irish. Some were escaped slaves and free Blacks who saw Mexico, a nation that had outlawed slavery, as a freer country than the United States, and who fought against the expansion of slavery. Others were Catholic immigrants from other countries such as Germany, Poland, and France who resented anti-catholic discrimination in the United States. This only ratcheted up as the predominantly Protestant US prepared for war with the overwhelmingly Catholic nation of Mexico. Still others were attracted by generous land grants that Mexico offered to foreign nationals who enlisted in the Mexican Army. Whatever attracted them, this predominantly Irish fighting force became one of Mexico’s most competent units in the Mexican-AmericanWar.
On September 21, 1846, the San Patricio Brigade saw their first action as an individual artillery unit, when they defeated American forces in three separate engagements during the Battle of Monterey. Their success in this battle encouraged more American soldiers to defect and join the San Patricio Brigade, whose numbers swelled from about 200 to 700 following the conflict. It was at this point that they designed their signature battle flag, a green flag with a gold harp at the center, surrounded by shamrocks and bearing the words “Erin Go Bragh.”

The San Patricio brigade fought bravely in numerous battles. They took heavy casualties at the Battle of Buena Vista where official reports argued that they were “worthy of the most consummate praise because the men fought with daring bravery.” Despite supply issues and large numbers of casualties, the San Patricio brigade performed valiantly until August 20, 1847. At the Battle of Churubasco when other Mexican units decided to surrender because they were outnumbered. When their Mexican comrades raised a white flag, the San Patricio Brigade shot at them, refusing to surrender until all hope was lost. Eventually, however, 80 members of the San Patricio Brigade surrendered to US forces.
After their capture, the US Army tried the San Patricio Brigade as deserters. Their two mass trials, which were carefully managed by General Winfield Scott, were held a mere 3 and 6 days after their capture. At the trials they were denied access to legal counsel and no transcript was made to document the procedures. 50 men were sentenced to death and executed by the United States military as it captured Mexico City.

The most brutal of these mass executions was the group hanging that Harney carried out on September 13, 1847. Harney, claiming “I was ordered to have them hanged and have no orders to unhang them” left the corpses of the 30 hanged men to decay on the gallows as a macabre warning to Mexico City residents who might resist American forces. Despite this violent display, irregular militias and individual Mexicans resented the American occupation of their country and guerilla forces regularly fought back against the Americans until the Treaty of Guadalupe Hidalgo was signed on February 2, 1848. Under the terms of the treaty, Mexico recognized Texas as part of the United States and ceded part or all of California, Colorado, New Mexico, Utah, Arizona, Nevada, and Wyoming.

As these conquered territories were incorporated into the United States, military commanders, including William Harney, violently seized Native American homelands for white settlers. During the Pig War, Harney and Winfield Scott, who had worked together to execute the San Patricio Brigade, violently disagreed over whether aggressive action was the appropriate way to settle the boundary dispute between the United States and Great Britain. Harney left Mexico just six weeks after he executed the San Patricio brigade, while Scott stayed for many months. During this time, Scott witnessed the toll of guerilla warfare and gained a great appreciation for the power of diplomacy in solving complicated international disputes.

Today, the San Patricio Brigade are regarded as national heroes in Mexico and Ireland. In Mexico City's San Jacinto Plaza a plaque commemorates the San Patricio Brigade, and a squad of Mexican bagpipers plays a monthly tribute to their service. In Clifden, Ireland, where the San Patricio Brigade’s commander was born, a statue honors the San Patricio Brigade, and the city flies the Mexican Flag annually on September 12 to celebrate this history. In 1997, the 150th anniversary of the San Patricio Brigade’s creation, Mexico and Ireland issued identical stamps bearing the flags of both nations to pay tribute to their history and legacy. Despite orchestrating their execution in order to discourage desertion, the United States Army denied the existence of the San Patricio Brigade until 1915, when a congressional inquiry revealed the coverup of their history.