No, it wasn't.
In the Texas Revolution of 1835-36, American colonists in Texas secured the independence of that area from Mexico and subsequently established a republic. Since the 1820s many settlers from the United States had colonized Texas; by the 1830s they far outnumbered the Texas Mexicans. Mexican dictator Antonio Lopez de Santa Anna attempted to reverse this trend by such measures as abolishing slavery. The settlers rebelled (originally as part of a general federalist resistance to Santa Anna's Centralist government, which had overthrown the Mexican Constitution of 1824). Hostilities began at Gonzales on Oct. 2, 1835; the Texans repelled a Mexican force sent to disarm them and won subsequent victories.