Several months previously, Texians had driven all Mexican troops out of Mexican Texas. About 100 Texians were then garrisoned at the Alamo. The Texian force grew slightly with the arrival of reinforcements led by eventual Alamo co-commanders James Bowie and William B. Travis. On February 23, approximately 1,500 Mexicans marched into San Antonio de Béxar as the first step in a campaign to retake Texas. For the next 10 days, the two armies engaged in several skirmishes with minimal casualties. Aware that his garrison could not withstand an attack by such a large force, Travis wrote multiple letters pleading for more men and supplies from Texas and from the United States, but the Texians were reinforced by fewer than 100 men because the United States had a treaty with Mexico, and supplying men and weapons would have been an overt act of war.