Using a brilliant artillery tactic, Zachary Taylor drove the Mexicans into the Rio Grande in the opening battles of the Mexican-American War.

On the northern edge of modern Brownsville, Texas, lie the battlefields of Palo Alto and Resaca de la Palma. It was here, on succeeding excessively hot days in 1846, that two still young countries clashed over their national borders. For the United States, only 70 years after declaring in- dependence, the clashes—the first of the Mexican-American War— were answers to the impatient summons of Manifest Destiny. For Mexico, just 25 years freed from Spanish rule, they resulted from a proud determination to maintain ancient boundaries. The armies that met on these battlefields together numbered fewer than 6,000 soldiers, but the repercussions of their fight would significantly alter the borders and futures of both nations forever.

General in Chief Mariano Arista commanded Mexico’s Army of the North. He began his military career at age 15 when he served as a cadet in Spain’s Regimiento Provincial de Puebla; four years later he was a lieutenant colonel. Supporting Mexico’s independence, he became a brigadier general under Mexican colors and soon had to choose sides in the power struggles over national leadership. Backing the wrong candidate in 1833, Arista was exiled to the United States, where he studied agriculture. Three years later, with a change in government, Arista returned and quickly became one of his nation’s military leaders. Experienced at handling large formations, Arista was a resourceful field commander willing to take risks, though he constantly worried about the generally poor condition of his conscript army. Blessed with an excellent eye for terrain, he would twice force the Americans to fight on ground of his choosing.

The experience of the American commander, Brig. Gen. Zachary Taylor, was largely confined to leading small units against irregular forces. Twenty-three years old when he joined the United States Army, Taylor had seen action in the War of 1812, as well as the Blackhawk and Second Seminole wars. Unhappy with American policy in Florida (where, he said, “an officer who has any regard for honesty, truth, or humanity, has but little to gain, and everything to lose”), Taylor was given a roving commission before his assignment in 1844 to Fort Jesup in west central Louisiana, where he took command of all United States troops in the Southwest.

While Taylor’s personal courage was never questioned, he struggled constantly to manage a large, untrained force at the far end of a logistical chain. In the coming battles he would make mistakes aplenty, enough to cost him victory several times over. In the end, his salvation would not be his knowledge or his experience, but an open mind and the stunning debut of a new artillery tactic.

As far back as Thomas Jefferson, the United States had tried to lay claim to Texas through purchase or diplomacy; first dealing with Spain and, after 1821, with a self-governing Mexico.

A complex accord became even more challenging when resident Texans successfully fought free of Mexican control in 1836, negotiating a settlement that left the actual boundaries between the two countries unresolved. Texans claimed the Rio Grande was the dividing line, while Mexicans insisted that the Nueces River, some 100 miles to the north, represented the historic border.

Texas leaders had hoped that annexation to the United States would quickly follow independence, but for several American presidents (Andrew Jackson, Martin Van Buren, and John Tyler) the knotty issue of slavery made it impossible to get the necessary congressional votes. Then James K. Polk took office on a promise to add Texas to the Union. Even before he was inaugurated, a deal had been made in Congress (in February 1845) that approved annexation. What Washington saw as a peaceful expansion was viewed in Mexico City (where Texan independence had never been accepted) as a provocation.

The unanimous vote to approve the union by a special Texas convention in mid-June triggered the events leading to the Palo Alto and Resaca de la Palma battles. Alerted as early as January to prepare for such a circumstance, the United States had increased its forces at Fort Jesup to some 2,000 soldiers. Taylor’s “Army of Observation” began departing in early July, its vanguard landing on July 25 near Corpus Christi, Texas, at the mouth of the Nueces River. While Mexican and American diplomats wrangled unsuccessfully, Polk funneled additional troops to Taylor from posts around the country until he had 4,300 regulars under his command, slightly more than half the nation’s entire standing army. By all accounts, Taylor used the time to drill his men in the large-formation tactics that most of his officers (51 of whom were destined to become Civil War generals) had only read about in books.

Once the talks collapsed, complicated by a January 1846 coup in Mexico City, Taylor was ordered to secure the Rio Grande border. His force (now designated an “Army of Occupation” by Polk) began decamping from Corpus Christi on March 8, to secure the region to the Rio Grande. Foot soldiers, mounted infantry (dragoons), and light artillery moved overland; heavy weapons and supplies were brought up by sea.

Because of problems finding adequate water, the three American brigades marched a day apart, with an advance guard one day ahead of them. Taylor’s objective was to reach the Rio Grande opposite the Mexican town of Matamoros, where Gen. Francisco Mejía commanded a small outpost force.

Other than bluffing the American columns with harassments at times, Mejía awaited Mexico City’s instructions, offering no real resistance. On March 24 Taylor’s land column (now combined) linked up with the seaborne component at the coastal village of Point Isabel, which became the main American supply depot for operations.

Leaving behind two artillery companies under Maj. John Munroe to garrison the depot, Taylor continued south on March 28, covering the 10 miles to the Rio Grande that same day. There he displayed the Stars and Stripes from a flagpole made of two wagon tongues lashed together, and began constructing a star-shaped, earthen-walled strongpoint he named Fort Texas. General Mejía built earthworks for his cannons and merely observed the goings-on across the river. Except for a spike in desertions from the American ranks by about 100 soldiers (disaffected Irish and German-speaking foreigners, for the most part), a sullen standoff ensued.

All was not tranquil, however, for at least one large band of Mexican irregulars was operating in the area. Mexicans killed a popular quartermaster officer and ambushed several patrols.

On April 11, Maj. Gen. Pedro de Ampudia relieved Mejía. He promptly ratcheted up tensions by sending Taylor a formal demand to withdraw his army. Taylor declined and instructed the American ships patrolling the mouth of the Rio Grande to institute a blockade. Ampudia, known more for his cruelty than his generalship, was trying to organize a first strike (then against Mexico City’s wishes) when General Arista arrived on April 24 to take charge of the Army of the North. He bore a manifesto from Mexico’s president authorizing active operations in what was termed “a defensive war.”

Arista realized that Taylor’s army was wholly dependent on the Point Isabel depot for food and ammunition. One day before his arrival, he ordered 1,600 men (cavalry, sappers, and light infantry) under Brig. Gen. Anastasio Torrejón to march 14 miles upriver to the village of La Palangaña. After fording the Rio Grande there, they would swing east to cut the Point Isabel road near a major trail intersection and watering hole known as Palo Alto. Then, on April 30, Arista took 2,100 soldiers 13 miles downstream to Rancho de Longoreño, where he would cross and link up with Torrejón. (He left 1,400 troops in Matamoros under General Mejía’s command.) With his supply line cut, Taylor would have to fight to eat.

Aminor action at the beginning of Torrejón’s operation had a hugely disproportionate repercussion. One of his advance parties ambushed an American patrol, killing 11 soldiers. When Taylor learned of the incident on April 26, he immediately sent word to President Polk that “hostilities may now be considered as commenced.” Polk received the dispatch on May 9 and two days later, declaring that American blood had been shed on American soil, asked Congress to recognize that a state of war now existed with Mexico. Congress declared war on May 13, though key battles had been fought several days earlier.

In Texas, Arista’s plan went well at first. Torrejón’s riders cut the Point Isabel supply road on April 28, scattering a Texas Ranger outpost. Some scouts carried the alarm south, and Taylor belatedly realized that he had left his supply depot woefully vulnerable. It speaks to his personal control that he resisted any impulse to rush off (despite rumors that Major Munroe was under attack) before he was satisfied that the Fort Texas defenses were ready. Late in the afternoon of May 1, he marched north with his 2,300 regulars organized into two brigades, fully expecting a battle. His weary men halted for a short rest on the plain at Palo Alto at midnight, and then continued, covering 30 miles in 20 hours and reaching Point Isabel around noon on May 2, their guns unfired.

A small detail unhinged General Arista’s bold plan. When his troops reached Rancho de Longoreño on April 30 they found just a few boats to ferry them across the Rio Grande and it took more than a day for the Mexican main body to gain the opposite bank. Then, fearing a spoiling attack from Fort Texas, Arista also ordered Torrejón to leave the Point Isabel road to cover his crossing. So when the American column cleared Palo Alto in the early hours of May 2, it was pure luck that had allowed Zachary Taylor to pass along an uncontested route.

Whatever disappointment Arista may have felt when Taylor’s forces eluded his trap, he remained determined to bring them to bay. After detaching General Ampudia with 1,230 men to assist General Mejía in eliminating Fort Texas, Arista hurried his column of 2,500 to Palo Alto, arriving there about 24 hours after the last American had passed. Following a careful reconnaissance of the area, Arista decided to stage the Mexican army three miles to the south at Tanques de Ramireño, where there was better water and access to the regional roads. The movement was completed on May 5, two days after Mejía’s cannons and Ampudia’s men opened fire on Fort Texas.

The American commander, Maj. Jacob Brown, was confident that his garrison of 550 men plus 6- and 18-pounder artillery was sufficient. Arista prohibited Ampudia from making a direct assault since Arista believed the American garrison would run out of supplies in less than three days and saw no reason to work to gather fruit that would simply drop into his hands if he waited. So the siege of Fort Texas became a cannon fight. The Americans were able to suppress several of Mejía’s guns before deciding to preserve limited gunpowder and hunker down.

The fort’s earthen ramparts proved extremely resilient, and Mexican shells failed to breach them. Nine American soldiers were wounded, but amazingly there were only three fatalities, one being the unfortunate commander, Major Brown, who was mortally wounded on May 6. The fort would be renamed in his honor, as would the city that grew up around it afterward.

The sound of Mexican cannon fire could be heard at Point Isabel, adding urgency to Zachary Taylor’s resupply mission. Thanks to a bold Texas Ranger courier, Taylor knew on May 5 that his fort on the Rio Grande was holding out, allowing him time to strengthen the Point Isabel defenses before his troops departed on May 7.

For his return trip, Taylor brought along 270 supply wagons and a pair of 18-pounder siege guns. Not surprisingly, his fighting column (2,228 soldiers) covered just seven miles on the first day. Mexican scouts spotted the American movement early on May 8, but Arista refused to credit their report. Not until a second party confirmed what the first had seen did he break camp and order General Ampudia to rendezvous with him at Palo Alto. By the time Taylor’s column reached there, the Mexican army was positioned across his path.

Arista chose to fight on a two-mile-wide plain covered by green saw grass (also called cord grass). The plants were chest-high, brutally sharp-edged, and surprisingly flammable. Stands of trees that gave the place the name “Palo Alto,” or “Tall Timber,” bordered the broad field. Although flat to the eye, the prairie rippled with numerous shallow depressions and snippets of old river meanderings, especially along its western side. Arista positioned his army (by now, some 3,200 men) in a nearly mile-long line, running west to east and facing north, with cavalry on the flanks, and artillery interspersed among the infantry units. Just covering this line took every man, so there was no infantry reserve.

Well off his left flank, hidden in the mesquite, were 400 mounted local irregulars commanded by Brig. Gen. Antonio Canales Rosillo. For reasons never explained, they would play no role in the coming fight. To bolster morale, Arista rode along his line and was greeted by waving banners and cries of “¡Viva la República!”

After pausing alongside the Palo Alto pond to let his men fill their canteens, Taylor took up a half-mile-long line parallel to Arista’s, perhaps 700 yards distant, facing south. His deployment was complicated by the need to button up the wagon train. He protected it with valuable mounted units and some artillery. Taylor sent a small Texas Ranger detachment into the mesquite to cover his right flank, and then spread his infantry and artillery east, holding back one dragoon squadron as a reserve.

Only after he had positioned his forces did Taylor real- ize he had neglected to locate the Mexican artillery. When a party of dragoons failed to find the enemy guns, two nervy volunteers, Lloyd Tilghman and Jacob Blake, rode to within musket shot of Arista’s line to plot the emplacements. It would appear that Taylor planned to send his infantry forward to skewer the other side with cold steel. Before that phase began, gunners on both sides engaged in some softening-up exchanges. Much to Taylor’s surprise, this proved to be the battle’s deciding action. Plagued by poor gunpowder and lacking explosive rounds, the Mexican artillerymen watched most of their copper cannonballs skip so slowly into the American lines that the soldiers were able to dodge them.

For their part, the American artillerymen unveiled a new tactical unit that proved even more deadly than its designer had imagined.

The problem with field artillery was that once it was established along a line of battle, it was difficult to quickly reposition. Maj. Samuel Ringgold of the 3rd U.S. Artillery Regiment had a better idea: assemble units of light, highly mobile bronze guns with exceptionally well-trained crews. His artillerymen were capable of rapid movement, even faster deployment, and high rates of fire. He had drilled his men relentlessly for just such an occasion, and at Palo Alto these units, termed “flying artillery,” played a vital role.

The moment that various Mexican batteries announced themselves by firing, American artillerists (who had explosive rounds) swarmed to the spot and quickly laid down a heavy counterbattery fire. And unlike most emplaced cannons, which generally restricted themselves to gun-to-gun duels, only switching to antipersonnel rounds in self-defense, Ringgold’s cannoneers also targeted Mexican infantry formations, appearing suddenly before them and carving bloody rents through the lines at a rate of two or three rounds per minute.

General Taylor may not have known much about artillery tactics, but once he saw how effectively his gunners were operating, he suspended any infantry advance to let them continue. “To see them limbering and unlimbering, firing a few shots, then dashing through the smoke, and then to fire again with lightning-like rapidity, partly hid from view by dense clouds of dust and smoke, with their dark-red shirts and naked arms, yelling at every shot they made, reminded me of a band of demons rather than men,” one American infantryman recalled.

For more than an hour the Mexican formations endured this deadly pummeling. With his cavalry poised on either flank, it would seem that Arista was hoping for an enemy advance in the center, which would then allow his riders to envelop the Americans. When this didn’t happen, he ordered his left flank cavalry (1,000 lancers under General Torrejón) to turn the American right and wreck the supply train.

The heavy chaparral (shrubs and small trees) and undetected marshes fatally slowed the mounted attack. The 5th U.S. Infantry Regiment saw the wallowing riders in time to hustle into a blocking position and form a hollow square. The American formation repulsed two fierce Mexican charges. Before starting a third, Torrejón brought up a pair of 4-pounders to blast the massed infantry but Ringgold’s artillery came to the rescue, gallantly galloping into position to smother the enemy guns before they even deployed. By the time the third cavalry charge went forward, the 3rd U.S. Infantry had joined the 5th. Torrejón’s men never had a chance.

Smoldering artillery wadding set the saw grass aflame in several places, and by 4 p.m., dense smoke forced a pause in the action. During this lull, both sides repositioned their lines, moving them counterclockwise. American maps of the period, supported by more recent battlefield archaeological explorations, indicate Arista pivoted on his center, the left flank falling back as the right advanced, causing the entire line to turn almost 75 degrees. Taylor moved his line to face the Mexicans.

The smoke had cleared enough by 5 p.m. for the cannon duel to resume. During the pause, Taylor pushed his two 18- pounders well forward along the road where they shotgunned canister into the Mexican ranks. Torrejón’s riders foiled an American attempt to turn Arista’s left with 68 dragoons, flying artillery, and infantry. Arista charged again and failed to turn the American right flank. Then, according to one account, many of his foot soldiers demanded to charge the norteamericanos, “for they wished to fight hand to hand, and to die like brave men.”

The Mexican general attempted to roll up the American left with infantry and cavalry, but Ringgold’s gunners mashed them into a bloody gruel. All along the lines American artillery fire continued to chew up the Mexican soldiers and horses, though the Americans were not unscathed. It was during this latter phase that a Mexican 6-pound shot struck Ringgold, who was mounted and directing his guns. The cannonball killed his animal outright and mortally wounded the major, who died on May 11.

At about 7 p.m. the firing sputtered out. As some of Arista’s units were beginning to panic, he pulled his forces back a short distance to regroup, while Taylor bivouacked along the line of battle. During the night the Americans observed flickering torchlights move across the unforgiving saw grass as the Mexicans gathered their wounded. American losses were 15 killed, 43 wounded, and 2 missing. General Arista later put his number of dead at 252, with no indication of wounded or missing. Neither party got what it wanted. Taylor’s road to Fort Texas was still blocked, and the American army had been neither turned back nor destroyed.

At about 6 the next morning, May 9, the Mexicans began withdrawing, according to General Arista’s orders. Taylor’s men and their commander watched them go. There were ample reasons for the Americans to stay put. Even after the beating it had taken the previous day, the Mexican army remained a formidable force. Taylor had called for reinforcements 12 days earlier, and troops were expected at any time, so any delay might well change the odds in his favor. This was the opinion of the majority of the senior officers he summoned to his tent for an informal council of war.

Still, watching and waiting wasn’t his preferred mode of operation. In some accounts, he stepped out of his tent and put the question to a passing junior officer. “We’ve whipped them,” was the prompt answer, “and we can again.” Said Taylor, “That is my opinion.” The American army (about 1,800 strong) set out after the Mexicans not long after 1 p.m. Taylor learned from his mistakes by leaving behind the wagon train, protected by a scratch force of rear-echelon troops, and his heavy 18-pounders. Now he could make better time.

Arista decided to withdraw when he realized that the Palo Alto battlefield put him at a fatal disadvantage. As long as the Americans’ fast-moving cannons could range at will, his men would not be able to close to bayonet range. He believed he had found an arena five miles down the road to Matamoros where the American guns would be neutralized. It was a place where the passageway was hemmed in by a thick tangle of chaparral and trees, which limited off-road movement and provided ample cover from which riflemen could pick off the pesky American gunners.

Here too the road passed through a 10-foot-deep, 200-footwide ravine, a remnant of the Rio Grande’s ancient course, which created a strong natural moat. Mexicans called these isolated channels resacas and knew the area as Resaca de la Guerrero. The Americans called it Resaca de la Palma.

Arista positioned his infantry along both banks of the resaca, with sharpshooters in front. He held his cavalry in reserve, and established a four-gun battery across the road at the chokepoint where it entered the ravine.

Neither patience nor subtlety was Zachary Taylor’s strong suit. When the head of his column drew near the Mexican position at about 3 p.m., his only plan was to smash through the enemy roadblock. He first tried his flying artillery under Ringgold’s successor, Capt. Randolph Ridgely, by pushing the guns down the road with skirmishing infantry on either flank. Command-and-control became impossible in the thorny chaparral, and the off-road operation degenerated into a series of squad-sized actions, hand to hand for the most part, as isolated parties of Americans brawled with Mexican detachments.

At the same time, the cannoneers in the road were struggling. It was difficult to make out their targets through the heavy brush, and at one point the Mexicans even managed to slip a cavalry column almost on top of Ridgely’s gunners. Constant training paid its dividends as the Americans swiftly changed to canister rounds and blasted the lancers before they could close.

Taylor’s men were making progress, but it was a slog, and too slow for the general. He ordered Capt. Charles A. May’s two-company squadron of the 2nd U.S. Dragoon Regiment to charge up the gut.

May was willing but unsure of his direction. Captain Ridgely obliged by drawing enough fire that the Mexican batteries revealed their location, allowing the horsemen to gallop off, four abreast, on a mad charge down the road. Arista’s gunners were not as quick at reloading as Ridgely’s, and the American riders were suddenly in among the Mexican cannons.

One key to a mounted charge, however, is knowing when to stop. May’s dragoons were a good quarter-mile beyond the guns before he could turn them around. By then the supporting Mexican infantry had recovered and when May’s battered survivors returned, they were without the cannons but bearing the officer commanding the entire Mexican defense, Brig. Gen. Rómolo Díaz de la Vega, as prisoner.

An exasperated Taylor waved forward one of his reserve regiments, the 8th U.S. Infantry. “Take those guns,” he ordered Lt. Col. William G. Belknap, “and by God keep them!”

While it didn’t actually knock out the Mexican guns, May’s charge sufficiently degraded their performance so that Belknap’s regulars (closely supported by the 5th U.S. Infantry) were able to reach them without crippling losses. At about the same time, soldiers of the 4th U.S. Infantry found a trail that enabled them to flank Arista’s left. These proved to be the actions that broke the enemy’s nerve.

Already shaken and weary from the pounding they had taken at Palo Alto, skeptical of officers who failed to deliver them a victory, without a commander, and with their ears full of rumors suggesting treachery—even treason—at the highest levels, Arista’s hitherto steadfast soldiers began to crumble. In an instant, small areas of panic coalesced into a rout and they fled.

Arista spent most of the battle at his headquarters, not imagining that the Americans would press the issue so soon. Once aware of the unfolding debacle, he personally led an unsuccessful cavalry counterattack. Many of Arista’s soldiers crossed the Rio Grande, but a good number did not; some drowned, some were swept up by Taylor’s prompt pursuit, others were killed by fire from the still defiant Fort Texas. As one astonished ferryman recollected, “They came in flocks, running and crawling like turtles, and they fell into the water flat on all fours like turtles and never stopped till they were in the brush of the Mexican Republic.”

Taylor reported his losses at 45 dead, 98 wounded. Mariano Arista later recorded 160 killed and 228 wounded, not caring to estimate how many surrendered. In addition the Americans took cannons, standards, and infantry weapons of all kinds, along with Arista’s personal papers and his silver service. The tight-lipped Taylor reported to Washington, “Our victory has been complete.”

The standoff at Matamoros resumed until May 18 when Taylor forced a crossing and occupied the town. General Arista and his men abandoned much of their equipment and retreated inland. By the time the Army of the North was reassembled around the town of Linares, just 2,638 of Arista’s soldiers remained.

In contrast, Taylor suffered an embarrassment of riches as thousands of American volunteers arrived. (Their lack of discipline, undirected pugnacity, and frontier nihilism would vex him no end.)

Never again in this war would there be any military force composed solely of United States regulars. From here on, the generals would have to learn how to manage with volunteer units in the mix. That experience would come in handy 15 years later, when the vast majority of units fighting in the American Civil War would be state volunteers.

With the successes of Palo Alto and Resaca de la Palma, American control of the disputed land between the Nueces River and the Rio Grande was established. The United States was poised for a dramatic expansion of its borders that would reach the Pacific coast, all at the expense of Mexico, which would eventually surrender an area of 529,017 square miles— larger than France and Germany together.

For Zachary Taylor, there would be more campaigning, two more major battles at Monterrey in September and Buena Vista in February 1847, and, propelled into office by the luster of his victories, election as the 12th president of the United States.

Mariano Arista had to answer for his actions along the Rio Grande to a military board in Mexico City, but after hearing evidence, the judges ruled that he had acquitted himself honorably and that his men had fought to the best of their abilities. The exonerated Arista would also rise to the highest office in the land, serving as Mexico’s president from 1851 to 1853.


Originally published in the Spring 2010 issue of Military History Quarterly. To subscribe, click here