Until 1819, Americans were not permitted to settle in Texas. After the signing of the Adams-Onís Treaty, in which the United States recognized the southern boundary of the Louisiana Territory as the Texas border, Mexican officials decided to encourage American immigration to Texas. At the time, Texas was largely unsettled, and the Mexicans were incapable of controlling the Indian tribes that roamed most of Texas. The American settlers became an effective barrier to the Indians. In 1821, Mexico gained its independence.

Soon after Mexico's independence, Stephen Austin made a dangerous trip to Mexico City to confirm the agreement made by his father for colonizing part of Texas. Americans were granted the right to colonize Texas, with the only requirements being to be Catholic and swear allegiance to Mexico. By 1830, almost 20,000 Americans had settled in Texas. During this period, Mexico continued to be in turmoil. Santa Anna led an uprising against General Anastasio Bustamante, the last in a long series of rebellions. The American forces in Texas supported Bustamante and defeated all his forces in Texas.

Santa Anna ruled in the same despotic ways as his predecessor, and his rule was not accepted in Texas. He decided to solidify that rule by sending in forces led by his brother-in-law, General Cos. Committees of public safety were formed throughout Texas. Austin, who had been confined in Mexico City for two years, returned to Texas and stated that "war is our only recourse." Texans rallied around Austin, and Texan forces set off to meet Cos's forces. On September 20th, 1835, the first battle took place at Gonzales. There, 200 Mexican cavalrymen were met by 168 Texans. The Mexicans fled back to San Antonio.

Texan forces moved toward San Antonio and the main force of Mexicans. On October 9th, Goliad was captured. Near San Antonio, Jim Bowie, with an advanced force of 92 men, routed a force of 300 Mexicans. When the army arrived at San Antonio, Austin's forces had reached 1,100. However, Austin refused to attack. When he was relieved of command to be sent to the US to garner support, General Sam Houston took over the overall command of Texan forces, while Colonel Edward Burleson became the commander of the forces arrayed before San Antonio. Burleson refused to attack. On December 4th, after Burleson first announced and then called off the attack, Colonel Ben Milam walked in front of the ranks and announced, "Who'll go with old Ben Milam into San Antonio?" Ignoring Burleson, the Texans marched the next morning on San Antonio. Cos had set up his cannons with an excellent field of fire. The Texans, however, moved forward by burrowing through the houses until they were close enough to attack Cos's artillery. In four days of fighting, the Mexicans lost between three and four hundred men, while the Americans lost only 2 killed and 26 wounded. One of those killed was Milam. Cos was forced to surrender his army of 1,105.

Houston realized, however, that the war was not won and that Santa Anna was no doubt on the way with reinforcements. His honor was at stake. Much of Houston's army deserted him to begin an attack on Mexico against Houston's orders. Houston headed north to form a new army, and on his way heard that Santa Anna had crossed the Rio Grande with an army of 8,000. Houston ordered Colonel Bowie to San Antonio, where the abandoned mission called the Alamo was being guarded by Colonel Joseph Neill. Houston ordered Bowie to blow up the Alamo after removing any usable cannons. Neill left the Alamo as ordered, but Bowie, together with William Travis, remained to hold the fort.

On February 24th, Santa Anna and his complete army arrived at the Alamo and began their siege. It began with the Mexicans running up a blood-red flag signaling no quarter. The Americans had 183 men in the fort, not enough to even man all the ramparts. For eleven days the siege continued. Each time the Mexicans attacked, they suffered heavy casualties. However, it became clear that the Texan ammunition would soon be exhausted. Twice, messengers were sent out requesting help, but it was clear that no help was possible. On March 5th, Santa Anna prepared for his final assault. Legend has it that Travis paraded his forces on the parade ground and offered them the choice of attempting to escape or dying in the defense of the Alamo. He is said to have drawn a line in the sand and asked all those who wished to fight to step across the line. All, save for one man, Moses Rose, crossed the line, including Bowie, who was dying from a wound.

At 4 AM on the morning of the 6th, Mexican bugles sounded and heavy columns of Mexican troops attacked. The Texans managed to repulse two attacks, but on the third assault, the overwhelming number of Mexicans managed to overcome the defenses. Three women and one black slave were the only survivors. The day after the Alamo, Dr. Grant, who had led a force of 70 men into Mexico, was killed with all but two of his men.

Houston began organizing forces to oppose Santa Anna. He ordered James Fannin, who had four hundred men at Goliad, to join him at Gonzales. Fannin did not obey immediately. First, he sent two smaller groups on a mission in which they were all killed by forces commanded by Jose Urrea. Urrea then caught up with Fannin's main force at Coleto Creek on March 18th. After a fight, Fannin surrendered with a promise that his men's lives would be spared. When Santa Anna arrived, he overrode the agreement and ordered all the men killed. On Palm Sunday, March 27th, all 330 prisoners were taken out and killed.

Houston, meanwhile, followed a strategy of falling back, forcing Santa Anna to divide his forces as he went. Houston's men were not used to withdrawing, but the General managed by the power of his personality to get his men to follow. After weeks of withdrawing, Houston's men captured two Mexican dispatch riders, giving him the location of Santa Anna—one day's ride from Houston's forces. The Texans then set off.

On April 21st, Houston held a council of war. All but two of his officers voted to await an attack, but Houston ordered an attack at 4 o'clock in the afternoon, correctly assuming that many of the Mexican troops would be resting. At 4 o'clock, the Battle of San Jacinto commenced, with Texan forces marching off to the cheers of "Remember the Alamo." The Texan forces achieved tactical surprise and routed the Mexicans. 652 Mexicans were killed, and 208 were wounded. A total of 708 prisoners were rounded up, with fewer than 200 Mexicans escaping. Santa Anna was one of those who initially escaped but was soon captured by Texan forces. Houston was under pressure to hang him for the atrocities he committed, but he knew that an alive Santa Anna was worth more than a dead one. Santa Anna signed a peace treaty, which gave total independence to Texas.