In October of 1835, four troopers of the Alamo de Parras Company were sent to Gonzales to retrieve a loaned cannon. The four troopers were seized, so 90 more solders were sent but were fired on. This was the shot that started the Texas Revolution. The returning Alamo Company soldiers and others started to fortify the Alamo and the town of San Antonio, they dug trenches, put up stockades, reinforced the walls with dirt inside, and built dirt and log platforms with ramps to fire cannons over the walls.
There were about 500 Mexican troops defending the Alamo and more defending the town across the river for 55 days. After an attack on the town by the rebels, the Mexican troops left, and the rebels took over the fort and town. Surrendering on December 11, 1835, the Mexican troops left and the rebels took over the fort and town. Just over 100 men under Colonel James Neil were left to garrison the site, with men spread both in town and at the Alamo, with about 24 cannons.
The fort's engineer, Captain Green B. Jameson sent three maps and complex plans for improving the defences with large outer earthworks, however, General Sam Houston suggested the Alamo blown up and the cannon and supplies hauled away as the fort was not defendable. Lack of draft animals prevented this.
On February 23, 1836, troops of the returning Mexican army arrived in San Antonio and began bombarding the Alamo with cannon. At this time the fort was under the joint command of Colonel William B. Travis and James Bowie with about 150 men. On March 1, 32 reinforcements entered the fort. Conflicting records exist as to the exact number of defenders, totals ranger from as low as 189 or as high as 254.
After a 13 day siege, the Mexican army attacked before sunrise on March 6. Travis died on the north wall, Bowie in a room by the Main Gate in bed. By the end of the battle, all the Alamo's Defenders were killed, and their bodies were burned in pyres outside the fort. General Andrade was left in San Antonio in command of 1001 Mexican troops, while the rest of the Mexican army marched to the east. The remaining troops refortified the Alamo over three months.