The siege of Bexar (San Antonio) became the first major campaign of the Texas Revolution. From October until early December 1835 an army of Texan volunteers laid siege to a Mexican army in San Antonio de Béxar. After a Texas force drove off Mexican troops at Gonzales on October 2, the Texan army grew to 300 men and elected Stephen F. Austin commander to bring unity out of discord. The Texans advanced on October 12 toward San Antonio, where Gen. Martín Perfecto de Cos recently had concentrated Mexican forces numbering 650 men. Cos fortified the town plazas west of the San Antonio River and the Alamo, a former mission east of the stream.
By the time the Texans camped along Salado Creek east of San Antonio in mid-October their numbers had grown to over 400 men, including James Bowie and Juan N. Seguín, who brought with him a company of Mexican Texans. Bowie and James W. Fannin, Jr., led an advance to the missions below San Antonio in late October, while Cos brought in 100 reinforcement men. On October 25 the democratic Texans conducted a debate over strategy. Sam Houston, who had come from the Consultation government, urged delay for training and for cannons to bombard the fortifications. Austin and others won support to continue efforts at capturing San Antonio.
From San Francisco de la Espada Mission on October 27, Austin sent Bowie and Fannin forward to Nuestra Señora de la Purísima Concepción de Acuña Mission with ninety men to locate a position nearer the town for the army. There on the foggy morning of the twenty-eighth Cos sent Col. Domingo de Ugartechea with 275 men to attack the advance force. The Texans drove off the assault from a position along the bank of the San Antonio River, inflicting over fifty casualties and capturing one cannon. Austin arrived after the battle of Concepción to urge an attack on San Antonio but found little support among his officers.
Cos then resumed defensive positions in San Antonio and the Alamo, while the Texans established camps on the river above and below the town and grew to an army of 600 with reinforcements from East Texas led by Thomas J. Rusk. After discussion among the Texan officers produced little support for an attack, some volunteers went home for winter clothes and equipment. Yet the arrival of more East Texans in early November offset the departures.
Texas and Mexican cavalry skirmished from time to time as the Texans scouted to capture Mexican supplies and to warn of any reinforcements for Cos. After a lack of early success, William Barret Travis led the capture of 300 Mexican mules and horses grazing beyond the Medina River on November 8. Four days later Ugartechea left San Antonio with a small cavalry force to direct the march of reinforcements from below the Rio Grande. Austin sent cavalry to intercept him, but the Mexican troops evaded them. Both armies suffered morale problems as a result of colder weather and limited supplies.
When three companies with over a hundred men arrived from the United States in mid-November, Austin again planned an attack. Officers still expressed doubts, however, and it was called off. Austin then left to assume diplomatic duties in the United States. The Texas troops selected Edward Burleson as their new leader.
When Erastus (Deaf) Smith reported approaching Mexican cavalry on November 26, Burleson ordered out troops to cut them off. Skirmishing followed near Alazán Creek west of town, with attack and counterattack by both sides. Finally the Mexican troops withdrew into San Antonio. The engagement became known as the Grass Fight because captured Mexican supply animals carried fodder for horses rather than the rumored pay for Mexican soldiers.
Because of limited supplies and approaching winter, Burleson considered withdrawing to Goliad at the beginning of December. Information on Mexican defenses from Texans who were allowed to leave San Antonio led to new attack plans. But fears that the Mexican army had learned of the assault brought a near breakup of the Texan army. When a Mexican officer surrendered with news of declining Mexican morale, Benjamin R. Milam and William Gordon Cooke gathered more than 300 volunteers to attack the town, while Burleson and another 400 men scouted, protected the camp and supplies, and forced Cos to keep his 570 men divided between the town and the Alamo.
James C. Neill distracted the Mexican forces with artillery fire on the Alamo before dawn on December 5, while Milam and Francis W. Johnson led two divisions in a surprise attack that seized the Veramendi and Garza houses north of the plaza in San Antonio. Mexican cannon and musket fire kept the Texans from advancing farther during the day and silenced one of their cannons.
That night and the next day the Texans destroyed some buildings close to them and dug trenches to connect the houses they occupied. On the seventh the Texans captured another nearby house, but Milam died from a sharpshooter's bullet. Johnson then directed another night attack that seized the Navarro house. On December 8 Ugartechea returned with over 600 reinforcements, but only 170 were experienced soldiers. Untrained conscripts formed the other 450 men, who brought with them few supplies. Burleson sent 100 men into town to join the Texan force that captured the buildings of Zambrano Row in hand-to-hand fighting. Cos ordered his cavalry to threaten the Texan camp, but they found it well defended. That night Cooke with two companies seized the priest's house on the main plaza, but they seemed cut off from the Texas army.
When Cos sought to concentrate his troops at the Alamo, four companies of his cavalry rode away rather than continue the struggle. Cos then asked for surrender terms on the morning of December 9. Burleson accepted the surrender of most Mexican equipment and weapons, but allowed Cos and his men to retire southward because neither army had supplies to sustain a large group of prisoners.
Texas casualties numbered thirty to thirty-five, while Mexican losses, primarily in the Morelos Infantry Battalion, which defended San Antonio, totaled about 150; the difference reflected the greater accuracy of the Texans' rifles. Most of the Texas volunteers went home after the battle, but Texas troops remained in town, which, with Cos’s withdrawal, left San Antonio and all of Texas under the Texans’ control.