GLENN: Mexico encouraged white settlers from the United States to populate the huge desolate area known as Texas. There were very few Mexicans there. No one knew how to deal with the natives, and they wanted the area settled to discourage the United States from annexing it.

So when Stephen F. Austin petitioned the New Mexican government, freshly independent from Spain to abide by his grant his father Moses had obtained from the Spaniards about bringing 300 American families in to colonize Texas, Mexico was initially excited about the idea. It was kind of like a job that Mexicans just wouldn't do.

However, the success of the movement overwhelmed the Mexicans, and they became concerned about losing the area entirely.

By 1829, tens of thousands of Americans had settled in Texas, with just a handful of Mexicans remaining there. They sent their trusted Mexican general to assess the problem.

The general reported back that Mexico had better stop the immigration from the United States. Does any of this sound familiar? Or they'd lose Texas forever. Anglo-Texans outnumbered the Mexicans there by a 10:1 margin.

Mexico responded by passing laws that ended immigration to Texas and imposed new taxes and new tariffs. The Texans, or Texians as they were called, widely resented the new laws. And in 1832 and '33, held conventions to draw up a new Texas constitution, modeled after the Constitution of the United States.

After the convention in 1833, Stephen F. Austin decided he was going to set off for Mexico City. And he was going to present the Constitution and the proposal for Texas independence to the Mexican government, and they're going to love this.

They didn't love this.

VOICE: In Mexico City, Austin had first seemed to think that things were going very well. He had met with Santa Anna. With General Antonio López de Santa Anna and had the sense that Texas would be granted more autonomy. Then he wrote an indiscreet letter from Mexico City, suggesting that whatever happened, Texas ought to take initiative and secure its own autonomy.

VOICE: Austin's letter was intercepted, and he was put in jail in Mexico City. He would be kept there for nearly two years. Upon his return, he had formed strong opinions of Santa Anna and the Mexican government.

VOICE: Santa Anna is a base, unprincipled bloody monster. War is our only recourse.

No halfway measures, but war in full. Stephen Austin, 1835.

GLENN: By 1835 relations had hit a fevered pitch.

Years earlier, Mexico had given a six-pound cannon to the residents of the city of Gonzalez, Texas, to help them deal with the attacks from the Comanche Indians.

Now, in retrospect, giving that cannon to fired-up Texans kind of seemed like a bad idea. So they asked for that cannon back. The residents of Gonzalez said, "I don't think so."

The Mexicans demanded the cannon back. Their defiant answer was, "Come and take it."

While Santa Anna's troops tried to do just that, and they were soundly beaten back by the militia in Gonzalez who used the cannon against them.

Now, because of his prior experience under Andrew Jackson in the war of 1812, the Texians appointed former Tennessee governor Sam Houston as their commander-in-chief of their forces. But there was only one problem: They didn't have any forces.

But like Texans usually do: They just pressed on.

VOICE: On March 2nd, 1836, delegates finally met at Washington on the Brazos and declared independence from Mexico. Sam Houston was instrumental in helping draft the new republic of Texas Constitution. And finally, it seemed that a workable government might actually be constructed.

GLENN: That's when Santa Anna gathered an army of 4,000 had to 5,000 troops and headed north to put down the rebellion. The war was on.

A small contingent, many from Gonzalez stayed in San Antonio, against the better judgment of Sam Houston to defend the Alamo. Houston thought it was indefensible and thought it was really foolhardy to stay. But the contingent had been joined by two American frontier heroes, one of them was Jim Bowie who had moved to Texas in 1830 and joined by the legendary Davy Crockett.

Crockett had recently been defeated in an attempt for another term in the United States Congress and left Congress and then Tennessee. And he said just before he left, "I told the people of my district that I would serve them as faithfully as I had done. But if not, they might go to hell. And I would go to Texas."

There were only 183 men defending the mission at the Alamo. Still, they kept that Mexican army at bay, of 5,000 troops for 13 days.

Then...

VOICE: At dawn of March 6th, 1836, 4,000 of Santa Anna's Mexican troops besieged the Alamo and killed all 183 Texans defending it. The battle was over in 90 minutes.

Another deadly siege for the Texans would ensue. This time at the mission of Goliad under the command of Colonel James Fannin.

VOICE: Fannin makes an attempt to withdraw. It's too slow. He's caught out on the open prairies, forced to surrender. The Mexicans marched them back. And a week later, under Santana's orders, the entire Goliad command is executed at the so-called Goliad Massacre.

GLENN: The defenders of the Alamo fought ferociously, with reports that they took 600 to 1500 Mexican soldiers to the grave with them. However, 400 more Texan militia men were slaughtered execution-style at Goliad, enflaming and enraging every man, woman, and child who heard the story.

Independence for Texas seemed nearly impossible now. Two massacres, and General Sam Houston in full retreat. For weeks, he continued to allude Santa Anna, waiting for the right time. Starting with an army of 300, but by late April, there were so many enraged Texans that were joining his army which had now grown to just over 900 men.

Houston managed to avoid battle with Santa Anna's large army for over a month, until finally both armies wound up near what is present day Houston, Texas. The date, April 21st, 1836.

Two armies camped at San Jacinto. Yes, that's the right way to say it in Texas. They were on the bayou about a mile away from each other, about to make military history. 3:30 that afternoon, the angry Texans were in a frenzy.

VOICE: The rebels advanced (phonetic) on the Mexican barricades, screaming like banshees their battle cry: Remember the Alamo! Remember Goliad!

Flustered, disoriented, the Mexicans began to fall back. First as individuals, but then as entire squads.

VOICE: For 18 minutes, blood and carnage ruled the battlefield at San Jacinto.

VOICE: I sat there on my horse, and I shot them until my ammunition gave out. Then I turned the butt end of my musket and started knocking them in the head. Private William Young.

VOICE: Mexicans fired one volley most of which went over the heads of the Texans. That's when Houston was hit. And his horse was hit. The Texans then advanced to maybe 20 yards away. They fired and then charged and broke through.

VOICE: All discipline was at an end. We fired as rapidly as we could. As soon as we fired, each man reloaded, and he who got his gun ready first moved on without waiting for orders. Private Alfonso Steele, 1836.

GLENN: The ragtag independence-minded Texas militia wouldn't be denied their chance to crush the Mexican Army.

VOICE: The Texans are in an absolute killing frenzy of revenge and fall upon any of the Mexican soldatos, some of whom begged for their lives, yelling, me no Alamo, me no Goliad. That finds them little mercy.

Most of the Mexicans actually fall back into a marsh area, into a lake. By the end of the day, Peggy Lake is completely crammed full of Mexican bodies, and the waters of Peggy Lake are thoroughly red.

VOICE: They had plunged into the mire and water with horses and mules. Everyone who seemed to escape, soon received a ball from the murderous aim of a practiced riflemen. And the bayou was literally bridged over with carcasses of dead mules, horses, and men.

Sam Houston, 1836.

GLENN: Meanwhile, there were just six Texan casualties compared to 600 Mexican soldiers dead, 700 more captured.

An hour after the carnage, Santa Anna himself was captured and brought before General Houston. Houston's men called out for execution. But Houston had something else in mind. Victory.

Victory and independence for the Republic of Texas, which the battle forced Santa Anna to sign.

The 18-minute battle still today one of the greatest and most incredible military victories in world history. And with it, the proud Republic of Texas was born.

Next time, the larger-than-life figures in the fight for Texas independence.