Roughly 1,500 Mexican troops under President-General Antonio López de Santa Anna arrived at San Antonio de Béxar and laid siege to a small garrison of Texian defenders holed up in the Alamo mission. The defenders, numbering fewer than 200, held out until March 6, when the compound was finally overrun, but their resistance bought time for Sam Houston's army and birthed the phrase "Remember the Alamo."
William Travis, the young co-commander of the garrison, reportedly drew a line in the dirt with his sword and asked every man willing to fight to the death to cross it—a story almost certainly embellished by later legend but true in spirit to what happened. Nearly everyone stayed.
Inside the walls were men like Jim Bowie, already famous for the knife that bore his name, and Davy Crockett, the former congressman who'd come to Texas after losing his House seat. Santa Anna raised a blood-red flag over the San Fernando church that first day, signaling no quarter would be given to the defenders.
The siege itself was largely an artillery duel and war of nerves, punctuated by a few skirmishes, before the final assault on March 6 killed nearly all the defenders. Santa Anna's brutality backfired spectacularly: six weeks later, Sam Houston's army crushed the Mexican force at San Jacinto in eighteen minutes, with soldiers screaming "Remember the Alamo!" as they attacked.