Palo Alto Battlefield National Historical Park | THE MEXICAN-AMERICAN WAR

The Mexican-American War

The Mexican-American War

Upon winning its independence from Spain in 1821, Mexico continued Spain’s policy of open immigration to its sparsely populated regions in what would eventually become the American southwest. Anyone willing to become a Mexican citizen and a Catholic was able to purchase land very cheaply, and since east Texas was the closest place in Mexico to the United States, that’s where the settlers first came. The Catholic requirement was changed to simply being Christian when the Mexican imperial government collapsed in 1823 and was replaced by a republic.

The way the immigration system worked was that one man, Mexican or otherwise, would be put in charge of an area for colonization. The man was called the empresario (a land agent), and it was up to him to then recruit Americans, Europeans, or Mexican families to settle in his colony. A minimum and maximum number of families was set in the contract, and the empresario had a certain number of years to meet the minimum requirement or else the contract would be terminated. The original American empresario was Stephen Austin, but there would be many more American and Mexican empresarios appointed by the Mexican government in the following years. By 1828 there were more immigrants than Mexicans in Texas.

There were a number of reasons why Americans came to Texas under Mexican control: there was no extradition, so they could escape debt and punishment for crimes in America; cheap land; promise of four years of tax-free income. Many Americans also moved to Texas because rumor had it that the United States would eventually buy the land, and that would make the land they purchased cheaply from the Mexican government more valuable since more Americans would now move west (the United States did offer to purchase the land, but Mexico was not interested). Whatever the reason, most hoped for a better life, though it is doubtful many took their oath of Mexican citizenship and religious obligations very seriously.

By the 1830s, the Mexican government had changed hands many times, and along with regime changes came changes in immigration laws. Settlers were becoming increasingly upset, and after a small rebellion in 1826 by one of the empresarios who had his contract cancelled, the Mexican government was becoming increasingly suspicious of the settlers’ true intentions. In response, the government passed The Law of April 1, 1830 (the actual name of the law), which severely limited immigration, instigated import taxes, and legally ended slavery, though keeping Americans from bringing slaves with them to desolate areas was nearly impossible to enforce.

In 1835, General Antonio Lopez de Santa Anna, who a year earlier had supported a Federalist government and the original 1824 Mexican Constitution that most settlers were happy with, took absolute control of the government and got rid of the 1824 Constitution, replacing it with laws that greatly limited states’ autonomy. Local militias were restricted and state legislatures were dissolved. This led to rebellions throughout Mexico, most of which were stopped abruptly by Santa Anna’s army. In September, the Mexican government began a military occupation of Texas.

All of these factors led to the settlers of east Texas taking up arms against the Mexican government, with fighting first occurring on October 2, 1835, in Gonzales (Texas independence wasn’t officially declared until March 2, 1836). Many people may not have heard of the Texas Rebellion, but most have heard of the Battle of the Alamo. This was a battle in the Texas Rebellion that the Americans lost, though they did eventually win the war in April 1826 after capturing Santa Anna in the Battle of San Jacinto. Santa Anna was forced to surrender in exchange for his release. All Mexican troops were to leave Texas and retreat over the Rio Grande River. While Santa Anna agreed to the terms, he was deposed during the time he was held captive. The new Mexican government did not stand by the treaty, but with the United States and many European countries now recognizing Texas’s independence, there was nothing Mexico could do about it without starting another war.

Within months of becoming an independent republic, Texans voted in favor of being annexed by the United States. However, the President Martin Van Buren administration did not want to start a war with Mexico, and many politicians did not want to admit a slave state without admitting a non-slave state, and there was no other potential non-slave state at the time. Texas withdrew its request for annexation in 1838.

In 1845, James Polk became president of the United States by campaigning under a platform of western expansion. His administration revived the possibility of Texas statehood, and Congress voted to annex Texas in February 1845. Great Britain did not want Texas to join the United States, so it brokered a deal with the Mexican government to recognize Texas as an independent country if Texas refused to join the union. However, Texas voted otherwise, and on December 29, 1845, it became the 28th state in the United States of America.

Not only did the Mexican government refuse to recognize Texas as an independent nation and later part of the United States, it considered the Texas territory’s border to be the Nueces River. Texas and the United States claimed the border as the Rio Grande River. Thus, the land between these two rivers as well as western Texas became a disputed region. Polk, with designs on the entire Mexican lands all the way to the Pacific Ocean, was looking for an excuse to take the land by force, but politicians and the American people would not stand for unprovoked aggression against Mexico. Thus, his administration hoped to draw Mexico into a war, but by having Mexico fire first. To do so, in early March 1846, troops under the command of General Zachary Taylor (a future president) were sent into the disputed territory to establish a fort—Fort Texas—on the Rio Grande River opposite the Mexican city of Matamoros. The results were exactly what Polk wanted.

The Mexican Army of the North under the command of General Mariano Arista marched over the Rio Grande to expel the Americans from the disputed territory. On April 25, 1846, 1,600 Mexican cavalry and infantry soldiers led by General Anastasio Torrejón came across an American 60-man scouting party under the command of Captain Seth Thornton at a ranch called Rancho de Carricitos about 25 miles west of modern-day Brownsville, Texas. A small skirmish ensued, and most of Thornton’s men were killed or taken prisoner. Total casualties on the American side were 11 dead and 46 captured, including Thornton. Little did anyone know at the time, but the Mexican-American war had just begun.

Knowing that the Mexicans had crossed the Rio Grande, General Taylor feared that Arista might move quickly to seize his supplies at Fort Polk, a U. S. supply depot at Point Isabel (now Port Isabel) on the Gulf of Mexico in Texas. Thus, on May 1, 1846, he departed Fort Texas for Fort Polk with 2,300 men. He left 500 at the fort under the command of Major Jacob Brown.

Realizing that the bulk of the American army had left the fort and that he had no chance of beating Taylor to Fort Polk, on May 3rd Arista launched an artillery attack on Fort Texas. The Mexicans continued the bombardment for the next six days, though after the first day the frequency of fire slowed tremendously on both sides. The Mexicans, realizing the bombardment was having little effect, and not wanting to charge the fort, opted for a siege in hopes of starving the Americans into surrender. But of course they would have to stop a rescue attempt by General Taylor and his men at Fort Polk.

Taylor could hear the shots from 50 miles away at Point Isabel, so he immediately knew what was happening. Arista was certain that the Americans would soon return to relieve the men at Fort Texas, so he marched his army (estimated 3,500 men) up the Matamoros Road to Palo Alto to block the Americans (the Matamoros Road connected Matamoros with Point Isabel). With over a thousand more men than Taylor, he was able to form a much wider battle line, which he anchored on both the left and right flanks with his very capable and experienced cavalry. Arista hoped for an infantry battle with the Americans going on the offensive with a charge, and if so, it was a simple matter of his cavalry outflanking and surrounding them.

Unfortunately for Arista, an American infantry attack never happened. When Taylor’s men came within 600 yards, the Mexicans opened fire with artillery. The Americans stopped, formed their own line, and returned fire. The entire battle ended up being an artillery dual.

The Americans had ten guns, including two large 18-pounders, the largest in the battle (pounder refers to the weight of the cannonball or shell that could be fired). These cannon were too heavy to move off the Matamoros Road and onto the softer terrain of the surrounding coastal prairie, so they remained in one place for the duration of the battle. The other guns were light artillery, mainly 6-pounders. Called the “flying artillery,” they could be quickly hooked up to horses and moved to wherever they were needed on the battlefield. Arista’s cavalry performed three flanking attacks during the fighting, and each time the flying artillery were maneuvered into place in time to repel the attack.

Replica of an 18-pounder cannon at Palo Alto Battlefield National Historical Park

Replica of an 18-pounder cannon at Palo Alto Battlefield National Historical Park

The Mexicans also had 10 guns, mainly 6-pounders and a couple of 12-pounders, but these were antiquated and their gunpowder was weak. As a result, most of their shots fell short of the target and bounced towards the Americans. One American soldier later wrote that they became very good at dodging bouncing cannonballs, though not everyone was quick enough to get out of the way—nine Americans died during the battle. The American cannon could also be fired more quickly than the Mexican guns. Arista himself estimated that the Americans fired 3,000 rounds to his 600.

Fighting began around 2 PM and ended at dusk five hours later. Both sides collected their dead and wounded as best as possible and settled in for the night. Arista felt that the open terrain at Palo Alto was no longer an advantage, so before dawn his men retreated five miles south on the Matamoros Road to a dry riverbed—Resaca de la Palma—that was lined with thick brush on either side. In the brush, not only were the men hidden from view, but they were also better protected from the American artillery that had soundly beaten them the day before at Palo Alto. The vegetation was so thick that Mexican soldiers had to use axes just to clear spots on which to stand. 

The next day, May 9, 1846, fighting began at Resaca de la Palma. This time the battle was a more traditional infantry and cavalry battle that Arista had hoped for, with much of the fighting being done with bayonets and fists. The artillery was used as well, but not as effectively as on the open terrain at Palo Alto. Even so, and despite the Mexicans still outnumbering the Americans, the battle results were the same. The fighting started around 3 PM, and within two hours the Mexican soldiers began fleeing back across the Rio Grande to Matamoros. American loses were 45 dead and 97 wounded, while the Mexican casualty total was 158 dead, 228 wounded, and 168 missing. Many men drowned while trying to cross the Rio Grande.

A victory at Resaca de la Palma ended the siege of Fort Texas. During the bombardment, two Americans were killed, one being Major Brown. The fort was subsequently renamed Fort Brown in his honor.

News of the fighting reached Washington two days later on May 11th. President Polk now had his excuse for war: American blood had been spilled on American soil. However, many politicians, including Abraham Lincoln, saw a war with Mexico for what is was—an excuse for a land grab. It wasn’t a war for resources, colonization, or because America needed more room for its population. It was just a war for greed. Blood had been spilled, but it was highly debatable if it was on American soil. Regardless of the opposition, enough members of Congress supported the Polk, and the United States declared war on the 13th.

The Mexican-American war continued until U. S. troops took control of Mexico City on September 14, 1847. The official end came on February 2, 1848, with the signing of the Treaty of Guadalupe Hidalgo. Mexico lost half of its territory while America gained all of present-day Texas, New Mexico, Utah, Nevada, Colorado, California, most of Arizona, and parts of Oklahoma, Kansas, and Wyoming. The United States did pay Mexico $15 million and forgave $3 million worth of debt.

For more information on the Mexican-American War, be sure to check out the following 17-minute video.

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Last updated on June 26, 2022
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