The Battle of Contreras, also known as the Battle of Padierna, took place on 19–20 August 1847, in one of the final encounters of the Mexican–American War, as invading U.S. forces under Winfield Scott approached the Mexican capital. American forces surprised and then routed the Mexican forces of General Gabriel Valencia, who had disobeyed General Antonio López de Santa Anna's orders for his forces' placement. Although the battle was an overwhelming victory for U.S. forces, there are few depictions of it in contemporary popular prints. The armies re-engaged the next day in the Battle of Churubusco.
Background
General Gabriel Valencia's army of the north was part of the forces that fought at the Battle of Buena Vista in February 1847, in which Santa Anna retreated before giving a crushing blow to the forces of Zachary Taylor. The Mexican forces were then divided in two, with one sent to Cerro Gordo and the other to San Luis Potosí. General Valencia was given the command of the forces in San Luis, replacing General Mora y Villamil. In April 1847 Battle of Cerro Gordo, General Winfield Scott's victorious forces clearly threatened the capital, and Valencia's forces were ordered to Mexico City. Most of Valencia's men were from Central Mexico, so the march southward brought them to their home territory. News that Scott's forces were marching from Puebla toward the capital was said to cheer Valencia's forces, who expected to be victorious. Valencia's troops marched rapidly south, from Texcoco northeast of the capital to Guadalupe Hidalgo, and traversed Mexico City on the way to their position south of the city in San Angel. They arrived in San Angel on August 17. Valencia expected the U.S. forces to attack San Antonio and anticipated his troops would move behind them to help bring about the victory. On 18 August, he placed a battery of artillery, overseen by General Mejía. Santa Anna did not concur with Valencia's positioning of his forces, and as Supreme Commander orders him to withdraw to Coyoacan and Churubusco. Valencia disobeyed Santa Anna's order and his disobedience "formed afterward his indictment" [in the defeat]. Santa Anna's plan for a coordinated defense of the capital fell apart when Valencia disobeyed his orders, essentially not recognizing Santa Anna as the commander of Mexican forces. Santa Anna and Valencia had a personal rivalry, one of many in the officer corps of the military and a product of years of coups and political rivalries.
The battle was the first one in the immediate environs of the capital, as part of General Winfield Scott's invasion of Mexico's heartland and drive to the capital. Leaving Puebla on 7 August for his march on Mexico City, the U.S. army under Scott, reached Ayotla and Chalco on 11 August with the divisions of David E. Twiggs, William J. Worth, John A. Quitman, and Gideon Johnson Pillow. Scott moved on the south side of Lake Chalco on 15 August, advancing to San Agustín. Rather than moving northward that would have taken them to the choke point at El Peñon, which Mexican General Antonio López de Santa Anna had fortified, Scott chose a circuitous southerly route to attack Mexico City. Santa Anna understood Scott's flanking action, and sought to block alternative routes into the capital. Santa Anna placed troops under his own command at the pueblo of San Antonio and commanded that the 7,000 men of General Gabriel Valencia's Army of the North, place itself at another strategic point at San Ángel, near Contreras by 17 August.
Battle
General Valencia had not yet faced U.S. troops in battle, and did not consider the spot that Santa Anna had ordered him to at San Ángel to be a defensible position. He disobeyed orders and moved his infantry and cannons to just south of Padierna. Valencia had not expected the U.S. forces to be able to cross the lava field at El Pedregal, considering it impassable terrain and a natural defense. Intending to flank San Antonio, Scott ordered Capt. Robert E. Lee to build a road across El Pedregal so he could enfilade San Antonio to the north of San Agustin. On the morning of 19 August, Lee's men met Mexican pickets, which Major William W. Loring's companies cleared at Padierna, only to come under fire from Valencia's 22 pieces of artillery west of El Pedregal and north of Contreras. When told of the American movement across El Pedregal, Valencia exclaimed, "No! No! You're dreaming, man." The U.S. forces took heavy casualties and Valencia thought at this point he was winning the encounter.