San Antonio was the most important town in Texas and the Texian rebels wanted to capture it. Stephen F. Austin marched to San Antonio with some 300 men in mid-October. Mexican General Cos decided to hold the Mexican position without fighting. The Texians began a siege to cut off the Mexicans’ supplies and communication. The Texans themselves had few supplies, and they had to hunt for food.
On October 27, militia leaders Jim Bowie and James Fannin, along with some 90 men, disobeyed Austin's orders and set up a defensive camp on the grounds of Mission Concepción. Seeing the Texians divided, Cos attacked. The Texians were outnumbered but drove off the attackers. The Battle of Concepción was a great victory for the Texians.
On November 26, the Texians heard that a new unit of Mexicans was approaching San Antonio. A small squad of Texians attacked, driving the Mexicans into San Antonio. The Texians discovered that the new unit was only men sent to cut grass for the animals trapped inside San Antonio. This “Grass Fight” helped convince the Texians that the Mexicans inside San Antonio were desperate.
Most of the Texian officers wanted to retreat. Many men wanted to attack, and still others wanted to go home. Only when Texan Ben Milam declared “Boys! Who will go with old Ben Milam into Bexar?” did everyone agree to the attack.
The Mexicans did not expect the attack, which began on December 5. The battle raged in the streets of the city. Two days later, the Texians began to show signs of winning the battle.
Mexican General Cos heard that relief soldiers were on the way, so he sent two hundred men to escort them into San Antonio. The men did not find any Mexican reinforcements coming, and they ran away in fear. This badly brought down Mexican morale.
Within days, the Mexican leaders had retreated inside the heavily armed Alamo. Mexican desertions and casualties were so high that the Texians now outnumbered the Mexicans in San Antonio.
Cos surrendered, and he and his men were allowed to leave Texas.
The successful capture of San Antonio was a big boost to the Texians. This was the rebels' second biggest victory in the Texas Revolution.
The leaders of the independence movement did not really want San Antonio because their homes were far away. Houston ordered Bowie to demolish the Alamo and abandon the city, but instead, Bowie fortified it. This led directly to the bloody Battle of the Alamo on March 6, in which 200 defenders were massacred.
Source: The Siege and Capture of San Antonio
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