It was William B. Travis who famously declared, "I shall never surrender or retreat." This declaration was made in a letter addressed to "The People of Texas and All Americans in the World," in which he urgently requested reinforcements for the besieged Alamo garrison. His determination to continue the fight even in the face of overwhelming odds has become an iconic symbol of the defenders' resolve during the battle.

As news of the siege spread throughout Texas, potential reinforcements gathered in Gonzales. They hoped to rendezvous with Colonel James Fannin, who was expected to arrive from Goliad with his garrison. On February 26, after days of indecision, Fannin ordered 320 men, four cannons, and several supply wagons to march towards the Alamo, 90 miles (140 km) away. This group traveled less than 1.0 mile (1.6 km) before turning back. Fannin blamed the retreat on his officers, but the officers and enlisted men accused Fannin of aborting the mission. He would later die at Santa Anna's hands after surrendering to Mexican forces at the Battle of Coleto Creek.

According to survivor Susannah Dickinson, when Travis realized that the Mexican army would likely prevail, he drew a line in the sand and asked those willing to die for the cause to cross the line. A bedridden Bowie requested that Crockett and several others carry his cot over the line, leaving only one man, Louis "Moses" Rose on the other side. Explaining that he was not yet ready to die, Rose escaped that evening.

After a thirteen-day siege, the Battle of the Alamo lasted only 90 minutes. After repelling two attacks, the Texans were unable to fend off a third attack. As Mexican soldiers scaled the walls, most of the Texan fighters withdrew into interior buildings. Occupiers unable to reach these points were slain by the Mexican cavalry as they attempted to escape.

According to the diary of José Enrique de la Peña, after the Mexican victory at the Battle of the Alamo, Manuel Fernández Castrillón brought before Santa Anna six or seven Texans who he had taken prisoner during the final assault, including Davy Crockett, who Castrillón spared when the final small band of Texans was overwhelmed. Santa Anna demanded that the prisoners be executed on the spot. When Castrillón and several other officers refused to carry out this order, staff officers who had not participated in the fighting drew their swords and killed the unarmed Texans.

When his father was about to ride to the Alamo with the relief force from Gonzales, William Philip King, only fifteen years old, persuaded his father that his family needed him more than Col. William Travis did and offered to go in his place. John G. King agreed to his son's request, and William reportedly manned a cannon at the Alamo before dying on March 6, 1836. King County was named in his honor.

Santa Anna's cruelty during the Battle of the Alamo inspired many to join the Texas Army. "Remember the Alamo!" became their rallying cry. In the Battle of San Jacinto, Sam Houston and the Texan Army engaged and defeated Santa Anna's Mexican army in a fight that lasted just 18 minutes. After being held for about three weeks as a prisoner of war, Santa Anna signed a peace treaty which dictated that the Mexican army leave the region, paving the way for the Republic of Texas to become an independent nation.

In 1838, during the Mexican retreat after a failed assault against French forces in the Pastry War, Santa Anna was hit in the left leg by cannon fire. His shattered ankle required amputation of much of his leg, which he ordered buried with full military honors.

The Alamo has had different owners over the years, including the Catholic Church, the Republic of Texas, and the city of San Antonio. In 2015, the Alamo Complex was transferred to the Texas General Land Office and the Alamo Endowment for restoration and management.

Today, the Alamo is a popular tourist destination with over 2.5 million people visiting the site each year. Visitors may tour the chapel, as well as the Long Barracks, which contains a small museum with paintings, weapons, and other artifacts from the era of the Texas Revolution.