Mexico won it's Independence from Spain and controlled Texas. They offered land to people who agreed to settle there in an attempt to increase settlement. Before long, Americans outnumbered the Tejanos.
Remember the Alamo!
The Alamo was a mission building.
In the Battle of the Alamo, Santa Anna's army attacked the Alamo, but were held at bay for 13 days by the defenders of the Alamo. Santa Anna's army eventually entered the Alamo and killed the defenders.
Remember the Alamo was a battle cry.
The Lone Star Republic is the nickname for Texas after the Texas Revolution.
Texas had to be a republic while they waited for a free state to come into the union so they could join the US as a state.