The Battle of Churubusco:

On August 20, 1847, American forces assaulted Mexico City as part of the ongoing Mexican-American War. After routing a large Mexican force under General Gabriel Valencia earlier in the day, the Americans were poised to take the bridge over the Churubusco River and enter the city. The bridge and a nearby convent were heavily defended, however, and taking the two enemy positions was very costly for the Americans.

The Mexican defenders, among them the St. Patrick’s Battalion, were eventually overwhelmed and surrendered when they ran out of ammunition.

The Approach to Mexico City:

By 1846, war between Mexico and the USA was inevitable. Mexico rankled over the loss of Texas, and the USA desired Mexico's western lands, such as California. After an invasion of northern Mexico did not succeed in making the Mexicans sue for peace, the US dispatched a second invasion force to land on Mexico's eastern coast and take Mexico City. This army, under General Winfield Scott, took Veracruz in April of 1847 and defeated the Mexicans at the Battle of Cerro Gordo on its way to Mexico City. By August, Scott and his army were at the very gates of Mexico City itself, which braced for the certain attack.

The Battle of Contreras:

In between Scott (approaching from the east) and Mexico City was a massive fort called El Peñon. Scott decided not to attack the fortress, instead moving his men around to assault the city from the south.

Meanwhile, Mexican General Santa Anna set his defenses in and around the city. He sent General Gabriel Valencia and some 7,000 men to San Angel to anchor the western end of the defensive line: Valencia (who had political aspirations and detested Santa Anna) instead took up a position near the town of Contreras, a little too far away from reinforcements. Seeing this, American General Persifor Smith attacked Valencia at dawn on August 20: the Mexicans were routed in less than 20 minutes, causing the whole Mexican defensive line to collapse.

The Battle of Churubusco begins:

Mexican soldiers, including but not limited to Valencia’s fleeing men, made a hasty retreat over the causeways into Mexico City. They even abandoned an eastern position which had only received a diversionary attack from the Americans. Seeing the Mexicans flee, the Americans swiftly pursued, hoping to capitalize on the rout. The Mexican forces holding the Churubusco bridge and nearby fortified San Mateo convent, however, did not immediately retreat: the Americans were running headlong into a heavily fortified position. The first assault on the causeway, led by Generals William Worth and David Twiggs, was successfully repulsed by the Mexican defenders.

Refusing to Surrender:

The Mexicans, enjoying a superior defensive position, held firm against the American attackers. The stiffest resistance came from the St. Patrick's Battalion, a Mexican army unit comprised primarily of Irish Catholic deserters from the US army: they had no illusions about their fate should they be captured. The Americans doggedly assaulted the bridge and convent, however, and Mexican pleas for more ammunition went unheeded. When the Mexicans ran out of ammunition, they tried to surrender: three times a white flag was raised over the convent, and every time one of the St. Patricks tore it down. In the late afternoon, the convent and bridge were both overrun by American forces.

Aftermath of the Battle of Churubusco:

Although Mexico City was before him and the Mexican defenses were in tatters, General Scott did not press the attack. Instead, he called for an armistice: he hoped that the Mexican leaders would see that the Americans held Mexico City in a checkmate and that they would negotiate without further bloodshed. Scott was wrong: although negotiations did begin, the Mexicans mostly used them as a stalling tactic to rebuild their defenses. About two weeks later, negotiations broke down and the US took control of Mexico City at the Battle of Chapultepec.

Taken together with the Battle of Contreras earlier in the day, Mexican losses - dead, wounded, captured and deserted - topped 10,000 on August 20, 1847. The victory was costly for the Americans as well: 139 killed and 876 wounded. It was the highest American casualty list of any one battle during the whole war.

Most of the St. Patrick's Battalion was captured or killed during the Battle of Churubusco. All in all 85 members of the Battalion were taken prisoner: of these men, 50 would be executed following two different courts-martial. 30 were hanged during the Battle of Chapultepec, at the very moment when the US flag was raised over the Chapultepec fortress. The leader of the St. Patrick's Battalion, John Riley, was not executed, but he was whipped and branded.

The Battle of Churubusco was important because of the great damage it did - in terms of casualties and morale - to the Mexican war effort. Although there were some bright spots - the spirited defense of the causeway and convent, for example - there was also plenty of bad news, such as Santa Anna's leaving Valencia exposed and not coming to his rival's aid. Although the armistice would buy Santa Anna time to review his defenses, the 10,000 men lost that day were simply too many.

To Mexicans, Churubusco was an important historical battle. The convent where the Saint Patricks fought is a historical monument and there is a plaque there to celebrate their bravery. In the US, the town of Churubusco, Indiana is named after it.

Sources:

Eisenhower, John S.D. So Far from God: the U.S. War with Mexico, 1846-1848. Norman: the University of Oklahoma Press, 1989

Hogan, Michael. The Irish Soldiers of Mexico. Createspace, 2011.

Scheina, Robert L. Latin America's Wars, Volume 1: The Age of the Caudillo 1791-1899 Washington, D.C.: Brassey's Inc., 2003.

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