American settlers in Texas came into conflict with Mexico in the 1830s over issues like religion, slavery, and self-government. This led Texians to declare independence from Mexico and form the Republic of Texas in 1836. The battle of the Alamo became a rallying cry, where around 180 Texians were killed after a 13-day siege by Santa Anna's army. Sam Houston then defeated Santa Anna at the Battle of San Jacinto, leading to Texas independence. However, the new Republic faced challenges like threats from Native American tribes, bankruptcy, and Mexico refusing to recognize its sovereignty.