De León joined his brother-in-law Plácido Benavides to fight with Stephen F. Austin at the 1835 Siege of Béxar.
[4] When Antonio López de Santa Anna revoked the 1824 Constitution of Mexico and installed his own political machine in 1833, many Tejanos were opposed to the regime.
Some of the De León extended family, specifically Benavides, Carbajal and brother Fernando, joined with John Joseph Linn[5] to fight Santa Anna's dictatorship.
In 1835, he joined the Benavides unit and fought under Stephen F. Austin during the two-month Siege of Béxar campaign to drive out Martín Perfecto de Cos.[7] Although many Mexicans were opposed to Santa Anna's regime, they were not necessarily in favor of Texas becoming an independent state.
[8] On July 20, 1836, Brigadier General Thomas Jefferson Rusk ordered Mexican families in the Victoria area to be evacuated in an attempt to stem any assistance being given to Santa Anna.
The Carbajal, Benavides and De León families left for New Orleans, forced to abandon their money and possessions.