Back around 1812 the Mexican government was encouraging foreigners to move in to the Texas area and offering them land at 12.5 cents an acre. This was cheap even then. They only had to agree to become Mexican citizens and Roman Catholics.
The vicious and evil General/President Santa Anna didn't like how things were shaping up demographic-wise and he reneged on that deal in the 1830s telling the Texan foreign settlers to vamoose.
The Texicans didn't like that one bit and they made a stand at the Alamo. 'Victory or death!' cried the Texans. There were about 150 Texans and several thousand Mexican soldiers at the Alamo. Santa Anna's surrender offer was rejected by the Texans so Santa Anna had his buglers play an eerie song that meant 'Take no prisoners!'.
After twelve days of cannon bombardment the Mexicans took the Alamo on the 4th assault and killed all the Texans, including Davie Crocket and Sam Bowie.
About 400 Texans later surrendered at Goliad under a promise of humane treatment, but Santa Anna changed his mind about that and had them all shot by firing squads.
At this point, the Texans were really good and pissed off. Three hundred of them caught 1400 Mexican soldiers taking a siesta on the banks of the San Jacinto River and killed 700 and captured the rest. 'Remember the Alamo! Remember Goliad!', they shouted, as they rained hot lead down on the sleeping troops. Nine Texans were also killed during this battle.
Later the Texans captured Genera Santa Anna and that was the ballgame. I'm not sure whether or not the Texans according him Geneva Convention protections. The fat guy with the microphone glossed that over.
The Republic of Texas was a sovereign nation for about twelve years until they voted to become a state. After a few years Texas went with the Confederacy and was admitted back into the Union after the Civil War.
