In 1835, big changes started happening in Mexico.

The country, which had won its independence from Spain in 1821 after more than a decade of fighting, The first constitution, known as the Federal Constitution of the United Mexican States of 1824 which inaugurated the First Mexican Republic, was repealed. A new constitution, Las Siete Leyes, was enacted in its place, creating the Mexican Republic which, under the head of President Antonio López de Santa Anna, was vastly different from the previous Mexico. Rather than emulating the United States, as it had previously done, this new Mexico sought to create a unitary republic, one focused around a centralized power. To do so, the new constitution contained several new policies, including banning slavery and tighter restrictions on immigration, as well as increased enforcement of laws and import tariffs. Santa Anna believed all of these changes would lead to a better, more stable Mexico.

The only problem? Most of his people didn’t like it.

Especially the Texans.

At the time, the area we now know as Texas was actually part of Mexico, and it was known as Mexican Texas. Although technically Mexico, it was home mainly to Americans, most of the residing in the border area illegally. This was never a problem under the old government. The federalists made special exemptions from Mexican law just for them, including allowing them to own slaves despite it being prohibited. Santa Anna’s new government, however, ended these exemptions and special statuses, insisting that these Texans adapt and become true Mexicans, subject to all laws and customs.

The Texans refused to comply.

Tensions continued to mount until October 2, 1835, when fed-up Texans refused to surrender a cannon, which had been loaned to the town of Gonzales for protection against native tribes, to Mexican troops who had been sent to recover it. Texans fired on the Mexican forces, who ultimately retreated.

And the Texas Revolution had begun.

Mexican troops within Texas were quickly overwhelmed, with the last group of them surrendering on December 9 following the siege of Béxar, where Texan soldiers captured the Mexican garrison at the Alamo Mission, a former Spanish religious outpost which had been converted to a makeshift fort by the recently expelled Mexican Army. Designed to withstand an assault by Indigenous attackers, not an artillery-equipped army, the complex sprawled across 3 acres (1.2 ha), providing almost 1,320 feet of perimeter to defend. An interior plaza was bordered on the east by the chapel and to the south by a one-story building known as the Low Barracks. A wooden palisade stretched between these two buildings. In other words, it was a ‘fort’ in only the very loosest sense of the word.

As time went on, many Texan fighters abandoned the cause, either due to their perceived victory or else because they were unprepared (or unwilling) to settle in for a long campaign. Whatever the case, by the time early 1936 rolled around, fewer than 100 troops remained at the Alamo.

Colonel James C. Neill, the acting Alamo commander, wrote to the provisional Texan government asking for supplies, but the government was in turmoil and unable to provide much assistance. Four different men claimed to have been given command over the entire army and, on January 14, Neill approached one of them, Sam Houston, for assistance. Houston could not spare the number of men necessary to mount a successful defense, but he sent Colonel James Bowie, along with a handful of men, to help out in whatever way they could. One of these was famous frontiersmen Davy Crockett.

Still believing the post’s vitality to Texas’s defense against the still-dangerous Mexican Army, Neill left the Alamo in early February, determined to recruit additional reinforcements and gather supplies. He transferred command to William Travis, the highest-ranking regular army officer in the garrison.

Unbeknownst to the Texas, while they were scrambling for provisions and men, Santa Anna had been quietly stewing…and on the move. Frustrated and embarrassed by his lack of success in the war so far, he continued to gather men at San Luis Potosí. His goal? To march to Bexar and retake the Alamo. The defeat there had been a personal one for Santa Anna; the disgraced troops run out of town by Texan fighters had been commanded by none other than Santa Anna’s brother-in-law, General Martín Perfecto de Cos.

On February 23, over 1,000 members of the Mexican Army began its siege on the Alamo. Over the next two weeks, the two armies traded gunfire, but there were few casualties. The Texans were both woefully unprepared as well as outnumbered, and yet they refused to cede their ground. There were reports that more than 200 cannonballs landed in the Alamo during the first week of the siege, which the Texans often reused, firing them right back at their Mexican counterparts. Despite Travis’s pleas for aid, none came. The Mexican Army, on the other hand, was replenished several times by reinforcements.

Just after 5:30 a.m. on March 6, 1836, 190 years ago today, Santa Anna began what would be the final assault on the doomed fort. Mexican troops breached the north wall and flooded into the compound, awakening many of the Texans inside. The fighting lasted 90 minutes, some of it hand-to-hand combat. Bowie and Travis were killed, as was Crockett, although reports differ as to exactly how and when. Several Texans reportedly surrendered, but Santa Anna ordered all prisoners be executed. Only a handful survived, mostly women and children. Historians estimate several hundred Mexicans died.

Unbeknownst to the Texas troops, as they were battling for their lives, newly elected delegates from across Texas were meeting at the Convention of 1836. On March 2, the delegates declared independence, forming the Republic of Texas. Four days later, the delegates at the convention received a dispatch Travis had written March 3 warning of his dire situation. Unaware that the Alamo had fallen, Robert Potter called for the convention to adjourn and march immediately to relieve the Alamo. Sam Houston, along with 400 men, journeyed to Gonzales only to be met with news that the Alamo had fallen.

On the afternoon of April 21 the Texan army attacked Santa Anna’s camp near Lynchburg Ferry. The Mexican army was taken by surprise, and the Battle of San Jacinto was essentially over after 18 minutes. During the fighting, many of the Texian soldiers repeatedly cried “Remember the Alamo!” as they slaughtered fleeing Mexican troops. Santa Anna’s life was spared, and he was forced to order his troops out of Texas, ending Mexican control of the province and bestowing independence on the new republic.

To this day, “Remember the Alamo” remains a rallying cry for Texans, who seek to never forget the blood and bravery that marked their journey to freedom.