Neill was promoted to lieutenant colonel during his participation in the siege of Béxar, and 10 days later Houston placed him in charge of the Texian garrison in the city. In January residents had begun evacuating ahead of Santa Anna's approaching forces. Neill pleaded with Houston for replenishment of troops, supplies and weaponry. The departure of Texians who joined the Matamoros Expedition had left Neill with only about 100 men. At that point Houston viewed Béxar as a military liability and did not want Santa Anna's advancing army gaining control of any remaining soldiers or artillery. He dispatched Bowie with instructions to remove the artillery, have the defenders abandon the Alamo mission and destroy it. Upon his January 19 arrival and subsequent discussions with Neill, Bowie decided the mission was the right place to stop the Mexican army in its tracks. He stayed and began to help Neill prepare for the coming attack. Lieutenant Colonel William B. Travis arrived with reinforcements on February 3. When Neill was given leave to attend to family matters on February 11, Travis assumed command of the mission, and three days later he and Bowie agreed to a joint command. Santa Anna crossed the Rio Grande on February 16, and the Mexican army's assault on the Alamo began February 23. Captain Juan Seguín left the mission on February 25, carrying a letter from Travis to Fannin at Goliad requesting more reinforcements. Santa Anna extended an offer of amnesty to Tejanos inside the fortress; a non-combatant survivor, Enrique Esparza, said that most Tejanos left when Bowie advised them to take the offer. In response to Travis' February 24 letter To the People of Texas, 32 militia volunteers formed the Gonzales Ranging Company of Mounted Volunteers and arrived at the Alamo on February 29.