The battle of Concepción occurred on October 28, 1835, the opening engagement in the siege of Bexar. After the skirmish at Gonzales on October 2 (the battle of Gonzales), the Texas army under Stephen F. Austin grew to 400 men as it advanced on San Antonio. Gen. Martín Perfecto de Cos, with a Mexican army that peaked in size at 750 men in late October, fortified the plazas in San Antonio and the Alamo mission (San Antonio de Valero) across the river.
On October 27 Austin ordered James Bowie and James W. Fannin, Jr., to lead ninety men from San Francisco de la Espada Mission to locate a protected position closer to the town. The four companies of Andrew Briscoe, Robert M. Coleman, Valentine Bennet, and Michael Goheen explored the other missions and briefly engaged Mexican scouts before reaching Concepción. There the officers decided to camp for the evening rather than return to the main army as Austin had directed. The Texans occupied a wooded bend in the San Antonio River protected by an embankment, and sent out pickets to warn of a Mexican attack. A few cannon shots from the town failed to inflict losses.
Cos seized the opportunity to attack the separate force the next day, sending out Col. Domingo de Ugartechea with 275 men and two cannons before dawn. The 200 Mexican cavalry drove in the Texan guards in early morning fog and formed on the west side of the river. Lt. Col. José María Mendoza led the smaller infantry and artillery forces across the stream to attack from the east. Mexican volleys crashed through the trees overhead, but inflicted no casualties among the Texans until Bowie moved Coleman's company to meet the advance. Then one man fell mortally wounded. The Texans responded with accurate rifle fire that drove back three Mexican charges and killed or wounded most of the infantry and artillerymen in about thirty minutes. Then the Texans counterattacked and captured one of the cannons. Mexican cavalry covered the retreat of the infantry and cannoneers who survived.
Austin and his other troops rushed to the field when they heard firing, but arrived too late to do more than hurry the Mexican withdrawal. Austin urged an assault on the town, but most of his officers believed San Antonio too well fortified. Mexican losses included fourteen killed and thirty-nine wounded, some of whom died later. Texas losses included one killed and one wounded.