The Battle of Churubusco took place on August 20, 1847, while Santa Anna's army was in retreat from the Battle of Contreras or Battle of Padierna during the Mexican–American War. It was the battle where the San Patricio Battalion, made up largely of US deserters, made their last stand against U.S. forces. The U.S. Army was victorious, outnumbering more than six-to-one the defending Mexican troops. After the battle, the U.S. Army was only 5 miles (8 km) away from Mexico City. 50 Saint Patrick's Battalion members were officially executed by the U.S. Army, all but two by hanging. Collectively, this was the largest mass execution in United States history.
 Following their defeats at Contreras, Antonio López de Santa Anna ordered Major General Nicolás Bravo Rueda with the Army of the Center, to retreat from San Antonio to Churubusco.: 296  Santa Anna also ordered Major General Manuel Rincón to hold the Franciscan Convent of San Mateo in Churubusco, with earthworks and seven guns, and placed General Francisco Pérez at the tête de pont on the south bank of the river.: 296  Two regiments were placed along the river while the convent included the Bravo Battalions of the Mexico City National Guard and the San Patricio Battalion, plus Santa Anna formed a reserve along the highway to the north.: 296 
 Scott sent David Twiggs and Gideon Johnson Pillow's Divisions from San Angel to Coyoacán, while he ordered William Jenkins Worth to turn the San Antonio position.: 296  Worth sent Colonel Newman S. Clarke's Brigade and Lieutenant Colonel Charles Ferguson Smith's Light Battalion across the Pedregal lava field to the west of San Antonio, while Colonel John Garland faced San Antonio on the south.: 297 
 During retreat from San Antonio, the Mexican defenders (part of the 1st Line of Defense (or sometimes the "Army of the Center") with Colonel F. Villarreal and about 2,000 men: 700 of the "Hidalgo," 500 of the "Victoria" (Lieutenant Colonel P. Jorrin) National Guards Battalions, and 800 others: under Colonels A. Zerecero and J.G. Perdigón Garay), were struck in flank by Clarke's Brigade. Garland moved forward as the Mexicans withdrew from San Antonio and captured a General and four guns.: 297 
 Scott ordered an attack on the convent.: 297  In addition to the stone walls of the convent, the defenses included a series of incomplete trenches the Mexicans had begun digging prior to the attack. Some elements of the Tlapa and Lagos Battalions arrived as reinforcements. Three cannon were placed on the right; two in the center; and the remaining two on the left. Independencia was assigned to defend the upper walls, the right flank leading to the bridge, the unfortified south and north sides, and two adobe huts further forward on the battlefield. The Bravos and the San Patricios were stationed on the left, behind barricades. In support along the Rio Churubusco was the Pérez Brigade: 2,500 men (11th Line, 1st, 3d & 4th Light Infantry Regiments).
 Worth's division took on the tête de pont, while Twiggs took on the convent.: 298  Rincón's gunners were able to force Taylor's battery to withdraw,: 298  and Perez's defense on the tête de pont twice repulsed Major Benjamin Louis Eulalie de Bonneville's 6th Infantry charge.: 298  The attack by Franklin Pierce and James Shields, crossing the river on the Coyoacan-Mixcoac road in an attempt to cut off the Mexican retreat, was also stopped.: 298  However, Worth turned the Mexican left and crossed the river, while the 8th and 5th Infantry took the tête de pont.: 300  Captain Duncan then set up a battery to attack the convent.: 300 
 Two of the Mexican cannons had melted and a third had fallen from its mount. Lieutenant Colonel Francisco Peñúñuri of Independencia led a handful of men in a bayonet charge and was defeated. He died in battle. Captain Luis Martínez de Castro, who had accompanied him, died of gangrene on August 27, 1847. Officers from the Bravos attempted to raise the white flag over the convent walls on three occasions: 300  but were prevented from doing so by members of the San Patricios, who had resolved to fight to the end and not let the Americans capture their flag. The San Patricio Battalion was ultimately captured and court-martialed for desertion, including its leader, John Patrick Riley. U.S. Captain James Milton Smith finally stopped the fighting by putting up a white handkerchief.: 300 
 The Americans captured 192 prisoners and three pieces of artillery at the tête de pont.: 300   They captured 1,259 prisoners, including three Generals and the San Patricios leader Lieutenant Colonel Francisco Rosenda Moreno, plus seven pieces of artillery at the convent.: 300  They captured another 380 prisoners further up the road.: 300  Winfield Scott estimated the Mexican casualties on August 19–20, at Contreras and Churubusco, at 4,297 killed and wounded; in addition to 2,637 taken prisoner.: 305 
 Seventy-two men of the San Patricios Battalion were court-martialed by the United States Army as deserters. Two separate courts martial were held, one at Tacubaya on 23 August, and another at San Ángel on 26 August. Fifty were sentenced to hang, having deserted after war had been declared. Those who had deserted earlier received 50 lashes. (See Saint Patrick's Battalion for a more complete description.)
 When General Anaya was asked by General Twiggs to surrender his ammunition after the end of the battle, he replied, "If I had any ammunition, you would not be here".
 Scott did not continue the pursuit into Mexico City, "...willing to leave something to this republic... I halted our victorious corps at the gates of the city.": 301 
 A Brigade of volunteers from New York was billeted to the convent, remaining there until September 7.
 Parts of the battle were portrayed in the 1985 ABC mini-series North and South, based on a trilogy of novels of the same name by John Jakes, as well as the film One Man's Hero (1999).
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