Mexican-American War

Preparation for war

Mexico entered the conflict with an army riddled by weakness and internal division. Of the nineteen states making up the Mexican federation, a mere seven contributed troops, weapons, and funding toward the fight. Concern about the nation's readiness was widespread among its leadership, and Santa Anna himself remarked that the army's leaders had done what they could to drill the rough volunteers who joined up, yet found it nearly impossible to instill in them any real devotion to the country they served. Lucas Alamán, a prominent conservative figure in Mexican politics, observed that funds poured into arming Mexican forces served mainly to let them turn on one another, creating merely the appearance that the nation possessed a defensive army. One officer, meanwhile, took aim at how Santa Anna had prepared the troops, noting that cavalry drills never went beyond the regimental level, that artillery units rarely maneuvered and never so much as fired a blank round, and that the commanding general himself was absent from field exercises, leaving him ignorant of what his various units could actually do. This same officer added that no one knew whether the top commanders ever gathered to discuss campaign strategy, or whether any plan for the campaign existed at all.

At the war's outset, Mexico's military was split into two categories: standing forces known as permanentes and militia units called activos. The permanent establishment comprised twelve infantry regiments (each made up of two battalions), three artillery brigades, eight cavalry regiments, a lone independent squadron, and a brigade of dragoons. The militia contributed nine infantry regiments and six of cavalry. Farther north, scattered frontier settlements relied on presidial companies, the presidiales, for protection.

Mexican soldiers carried leftover British muskets from the Napoleonic era, the Brown Bess among them. American troops early on were armed similarly, with flintlock Springfield 1816 muskets, though as fighting continued, more dependable caplock weapons gained favor. Certain American units wielded far more advanced arms that gave them a real edge, including the Springfield 1841 rifle used by the Mississippi Rifles and the Colt Paterson revolver carried by the Texas Rangers. Later in the war, Colt Walker revolvers went to the Mounted Rifles, a weapon the Army had ordered a thousand of back in 1846. Perhaps above all, American artillery's superior quality tipped the balance again and again throughout the fighting.

Writing his memoirs in 1885, former president Ulysses Grant, who had served in the war himself, pointed to Mexico's shoddy military organization as the root of its defeat. He described the private soldier as drawn from the poorest classes without any say in the matter, clothed badly, fed worse, rarely paid, and discharged once no longer needed. The junior officers, he wrote, stood only marginally above their men in quality. Yet Grant conceded that he had witnessed acts of bravery from these soldiers equal to any he had seen elsewhere. He noted that Mexico had since built an army larger than that of the United States, complete with a military academy patterned on West Point, staffed by educated and undoubtedly courageous officers, concluding that a war like that of 1846 to 1848 could no longer happen in his own time.

Political fracture within Mexico severely hampered its capacity to wage war. Centralist conservatives and federalist liberals struggled constantly for control, and on occasion factions within the Mexican military turned their weapons on each other rather than on the invading Americans. Santa Anna himself lamented, with evident bitterness, that however humiliating it was to say so, Mexico had inflicted this disgrace upon itself through endless internal fighting.

Mexican presidents during this period rotated through office in spans measured sometimes in months, sometimes in mere weeks or days. Just before hostilities began, liberal General José Joaquín de Herrera held the presidency from December 1844 to December

Outbreak of hostilities

Acting on Polk's directive, Taylor marched his forces toward the Rio Grande, brushing aside Mexican calls for him to pull back to the Nueces. There he threw up a hasty fortification across from Matamoros, Tamaulipas, a post that would come to be called Fort Brown or Fort Texas.

Mexico readied itself for conflict. On April 25, 1846, a Mexican cavalry force of 2,000 men fell upon a much smaller American patrol, seventy strong, under Captain Seth Thornton, who had been dispatched into the disputed strip of land lying between the Nueces and the Rio Grande. This clash, remembered as the Thornton Affair, ended in disaster for the Americans: eleven soldiers lost their lives and fifty-two were taken prisoner.

Not long afterward, on May 3, 1846, Mexican guns at Matamoros began shelling the new fort, launching what became a siege lasting 160 hours as enemy troops closed in from all sides. The defenders returned fire throughout. By the time the bombardment ended, thirteen Americans had been wounded and two lay dead, one of them Jacob Brown, whose name the fort would later bear.

Taylor set out on May 8 with 2,400 men to break the siege, but General Arista moved quickly northward with 3,400 troops and cut him off roughly five miles above the Rio Grande, near what is now Brownsville, Texas. Here the Americans put their so-called flying artillery to use, light guns mounted on horse-drawn carriages that let entire crews gallop into position. Mexican forces answered with cavalry charges and cannon fire of their own, though their powder proved inferior, sending shots so slowly that American troops could actually step out of the way. Shaken by the effectiveness of the U.S. guns, the Mexican army withdrew overnight to a dry riverbed, or resaca, hoping the terrain would favor them in the next clash. The position offered natural cover, but the retreat left Mexican units scattered and poorly coordinated.

The following day, May 9, brought the Battle of Resaca de la Palma, marked by brutal close combat. American cavalry seized Mexican cannon, breaking the enemy line and turning retreat into rout. Arista, fighting on ground he did not know well and watching his men scatter, could not restore order among his troops. Casualties on the Mexican side mounted heavily, forcing the abandonment of guns and supplies. As the beaten army streamed past Fort Brown, defenders there inflicted further losses, and still more Mexican soldiers drowned attempting to cross the Rio Grande. Taylor then pushed his own forces across the river, opening a campaign that would carry the fighting into Mexican territory.

News of the Thornton episode reached Polk, who paired it with Mexico's earlier rejection of Slidell to conclude that grounds for war existed. In his message to Congress he declared that patience had already run out even before word arrived from the Del Norte frontier, and that Mexico, after repeated threats, had crossed into American territory and spilled American blood on American ground, effectively announcing that a state of war existed between the two nations.

Congress took up the matter on May 13, 1846, and after only a few hours of discussion approved the declaration, with southern Democrats backing it firmly. Sixty-seven Whigs opposed a related slavery amendment, yet when the final vote came only fourteen stood against the declaration itself, John Quincy Adams among them. Later, newly elected Whig representative Abraham Lincoln of Illinois would dispute Polk's claim about bloodshed on American soil, denouncing it as a bold falsification of history.

Ulysses S. Grant, who opposed the war yet served under Taylor as a lieutenant, later wrote in his Personal Memoirs of 1885 that the true purpose behind advancing from the Nueces to the Rio Grande was to draw Mexico into striking first, thereby weakening any political resistance to war at home. He noted that simply stationing troops at the edge of disputed land, far from Mexican towns, would not be enough to spark a fight, and that provoking Mexico into firing the first shot was essential, since Congress might otherwise hesitate to declare war. Once Mexico acted, he observed, the executive could announce that war existed by her doing and pursue it vigorously, and few public figures would then dare object. Since Mexico showed no interest in driving the invaders back to the Nueces herself, it fell to the American army to move close enough to invite an attack. Preparations therefore

Written by Aubrey Research from Mexican-American War on Wikipedia, cited as a reference and not reproduced.

Where these engagements were fought

42 of the 68 could be placed to a location and appear on the map; the remaining 26 are recorded without a precise point. Select a marker to see the engagement.

Documented engagements

Plus 13 further documented engagements in the Mexican-American War record.

By state

Engagements and locations are compiled from published sources: Wikipedia (text rewritten and cited as a reference, CC BY-SA 4.0).