The American-Mexican War of 1846/48 (Part I)

The victory of Texas in the War of Texan Independence (1835/36) was inevitably a very severe blow to Mexican national pride. As long as Texas remained an independent state between Mexico and the USA, however, the Mexicans were prepared to swallow their pride and open war even though they refused to recognise the independence of Texas. Small-scale raids of considerable savagery were a constant feature of life on the Texan/Mexican border, and within Texas there were increasing demands for union with the USA. These demands were resisted by the USA mainly because the anti-slavery northern states saw the accession of Texas to the union as increasing the strength of the pro-slavery southern states.

In November 1844 President John Tyler learned that he was to be succeeded by James K. Polk, who had campaigned on the platform of the ‘Manifest Destiny’ of the USA to dominate the North American continent. Tyler took this as a mandate from the US people and pushed through the Congress a measure to admit Texas to the union. On 1 March 1845 the two houses of the Congress jointly admitted Texas, and Mexico immediately broke off diplomatic relations with the USA. Polk was inaugurated three days later. The new president still hoped that the USA would be able to negotiate with Mexico about the Texan question (as well as to buy Upper California), but anticipated trouble when Texas accepted American annexation on 4 July. On 23 March, therefore, Polk ordered Brevet Brigadier General Zachary Taylor to shift his forces from Fort Jesup on the Louisiana frontier to a tactical position in Texas near the Rio Grande so that he could repel any Mexican invasion.

Taylor chose a spot near the small town of Corpus Christi at the mouth of the Nueces river, and beginning on July 23 sent most of his 1,500-man force by steamship to establish a forward base. Taylor’s dragoons travelled overland via San Antonio, and as reinforcements continued to flow south Taylor had nearly 4,000 men under his command in mid-October. These included some New Orleans volunteers as well as a company of Texas Rangers used as scouts, while his 3,500 regulars constituted about two-fifths of the regular army’s authorised strength of 8,500 men as fixed after the 2nd Seminole War (1835/43).

For the next six months the Americans drilled and trained in an area which offered few if any creature comforts. In February 1846 negotiations with Mexico stalled, and Taylor was ordered to advance to the Rio Grande river. The American advance was a long column headed by Brevet Major Samuel Ringgold’s ‘flying artillery’ battery and tailed by 300 ox-drawn wagons. The ‘flying artillery’ had been created in 1838 at the personal order of Secretary of War Joel R. Poinsett as a high-mobility battery in which the men rode on horses rather than on the limbers and caissons. On 23 March the column reached a fork in the road, and here Taylor divided his force. Most of the men were sent down the right-hand road some 18 miles (29 km) to a position on the Rio Grande opposite Matamoros, where the Mexicans had gathered about 5,700 men. Taylor himself took a small detachment down the left-hand road the 10 miles (16 km) to the place at which he was to meet the force’s supply ships at Point Isabel. Here Taylor created his supply base, loaded his wagons and brought ashore the 18-pounder siege guns. Opposite Matamoros, Taylor’s camp quickly developed into Fort Texas, where the siege artillery was mounted.

The Mexicans maintained a constant stream of threats, and on 25 April open hostilities broke out only days after the arrival in Matamoros of General Mariano Arista with perhaps 3,000 Mexican reinforcements. The Mexicans launched a 1,600-man cavalry force across the Rio Grande and attacked a reconnaissance force of 63 dragoons under Captain Seth B. Thornton: 11 Americans were killed in the attack and the others, including the wounded Thornton, were captured.

Taylor reported to Washington that the war had effectively started, and called on Louisiana and Texas for reinforcements totalling about 5,000 militia men. Worried that the supply base at Point Isabel might be captured, and leaving Major Jacob Brown in command at Fort Texas with one infantry regiment and a detachment of artillery, Taylor departed on 1 May with most of his force to strengthen the defences of Point Isabel. On May 7 Taylor started the return journey to Fort Texas with 2,300 men, 200 ox-drawn supply wagons and two more ox-drawn 18-pounder guns.

Arista had crossed the Rio Grande with 6,000 men on the day that Taylor left Fort Texas and laid siege to the fort on 3 May. The siege by 1,500 Mexicans lasted five days. In the course of the fighting only two American casualties were suffered. One of them was Brown, and to commemorate his death Fort Texas later became Fort Brown, and the town that sprang up at the spot was then named Brownsville.

At about 12.00 on 8 May Taylor met the Mexicans at Palo Alto. The two forces lined up opposite each other on open ground that favoured the Mexicans’ larger force of cavalry, but overall superiority was provided by the US artillery. The 18-pounders were located in the centre of the American front and fired canister, while the 6-pounder guns and 12-pounder howitzers on the flanks fired shot and and shell respectively. Considerable damage was inflicted on the Mexicans by the artillery, and a cavalry charge was very severely handled. During the afternoon a burning gun wad caused a grass fire and, after hostilities had been suspended for one hour by the smoke, the Mexicans began to fall back. The armies bivouacked for the night, and in the morning the Mexicans retreated. American casualties in the Battle of Palo Alto were nine killed (including Ringgold) and 47 wounded, while the Mexicans had lost some 320 dead and 380 wounded.

Taylor delayed his advance until he had fortified a position for the wagons he intended to leave behind, and then reached the Mexicans at a dried river bed, Reseca de la Guerra. Here the Mexicans had improvised an entrenched position of some strength with ponds and dry chaparral protecting their flanks.

Taylor sent in the ‘flying artillery’, but this was checked by the Mexican guns and called for help that was provided by a dragoon detachment. This overran the Mexican guns but was then caught in musket crossfire and could not prevent the Mexicans from recapturing their guns. These were again captured by the Americans in the close-order infantry battle that developed, and the demoralised Mexicans soon broke, fleeing in disorder to Matamoros. The Battle of Resaca de la Guerra (often known as the Battle of Resaca de la Palma after the neighbouring dry river bed where Taylor first learned of the Mexican stand) cost the Americans 33 killed and 89 wounded, while the Mexicans lost at least 550 dead and wounded.

The Americans could not catch the Mexicans before they reached the Rio Grande, and by the time Taylor had brought up boats from Point Isabel to cross the river, Arista’s army had disappeared into Mexico.

On 13 May the Congress declared war on Mexico, and by raising the strength of companies from 64 to 100 men created the potential for an army with an enlisted strength of 15,540 men. The Congress also voted for a regiment of mounted riflemen as well as a company of sappers, miners and pontoniers (pontoon bridgers). The president was also authorised to enlist 50,000 volunteers for the duration of the war. The political objective of the war was the seizure of all Mexico north of the Rio Grande and Gila River as far west as the Pacific. The strategic plan designed to yield this result was the brainchild of Major General Winfield Scott, commander of the US Army, and matured as a three-pronged offensive. Taylor was to advance west on Monterrey, and so open the possibility for further advance into northern Mexico. Brigadier General John E.Wool was to advance west from San Antonio on Chihuahua, although this axis was later turned 90 degrees south to make Saltillo the objective. Colonel Stephen W.Kearny was to advance south-west from Fort Leavenworth on Santa Fe with the ultimate task of reaching San Diego in Upper California; part of Kearny’s force was later detached under Colonel Alexander W. Doniphan to move south from Santa Fe to El Paso and Chihuahua with the task of reaching Parras, just to the west of Taylor’s and Wool’s forces.

Polk thought that this would be ‘a brisk and a short war’. Events soon proved him wrong, especially when fourth prong of the offensive (an overland advance on Mexico City after an amphibious landing at Vera Cruz) had been added. Scott was never as optimistic as Polk, for he appreciated the problems posed by Mexico’s size and lack of communications, and also the country’s 30,000-man army. This last was not well equipped, but was well experienced in warfare after some 20 years of spasmodic revolution. Polk feared that Scott had political ambitions and decided that the general should not receive the advantages of command in Mexico. Polk therefore promoted Taylor to brevet major general and placed him in overall command of Mexican operations.

US troops marching on Monterrey during the Mexican-American War

The Monterrey Campaign
Taylor planned to move from Matamoros to Monterrey via Camargo, about 130 miles (210 km) up the San Juan river, using a force of about 6,000 men. At Camargo Taylor planned to establish a supply base and then strike out to the south-west toward Monterrey in the foothills of the Sierra Madre. No immediate start could be made because Taylor’s army lacked adequate transport for its supplies. Orders for wagons were placed in the USA even as shallow-draught steamboats were requisitioned from operators on the Mississippi and Ohio rivers. The steamboats started to arrive across the Gulf of Mexico during July, and by the end of the month Taylor had a force of 10 such boats. The wagons did not arrive until November, when the campaign was over, so Taylor was forced to rely on his existing wagon train of 175 vehicles, boosted by some locally procured ox-carts and 1,500 pack mules.

Manpower was no problem, for in May the first of the militia units requested by Taylor at the beginning of hostilities began to arrive. These Louisiana and Texas units were supplemented by large numbers of volunteers recruited for six months in neighbouring states by Brevet Major General Edmund P. Gaines, commander of the Department of the West. Gaines had done much the same thing in the 2nd Seminole War, and despatched some 8,000 men to Mexico before he was court martialled for exceeding his authority and moved to command the Department of the East. Only a few of these volunteers had signed for 12 months of service, but until they could be returned home the others had to be fed, accommodated and even clothed. In June another stream of men began to arrive, these being the volunteers authorized by the Congress.

By August Taylor had pushed 15,000 men up to Camargo, a low-lying spot that had recently been inundated and now, sweltering in the full heat of the summer, disease was breeding rapidly. Soon more than half the volunteers had been laid low by heat and disease, and when Taylor started the advance on Monterrey his strength had been reduced to 3,080 regulars and 3,150 volunteers. The regulars were reinforced with a few volunteers to create the 1st and 2nd Divisions, while the majority of the volunteers formed the Field Division even though the two regiments of mounted Texas volunteers liked to regard themselves as the Texas Division. More than one-quarter of Taylor’s army was mounted, these units having percussion rifles rather than the flintlock muskets of the infantry. Taylor was not a strong believer in artillery, despite the success of this branch at the beginning of the campaign. He had been warned that his four batteries of field artillery would be of little use against stone-built structures, but otherwise included in his artillery train only two 24-pounder howitzers and one 10-in (254-mm) mortar.

On 19 September Taylor’s army reached Monterrey, a stone-built city blocking the pass through the Sierra Madre to Saltillo. The city was held by General Pedro de Ampudia’s force of 7,000 Mexicans equipped with new 9- and 12-pounder guns of British origin rather than the obsolescent type of field artillery used at Palo Alto. The Americans camped outside the city and, after a reconnaissance had been carried out by parties that included engineers, attacked on the following day.

The city’s primary defensive feature was a citadel on its northern side, and other notable factors were a ring of forts and, to the city’s south, a river. Taylor’s first move was to send one of his regular divisions, led by 400 Texas Rangers, round the city to block the Saltillo road, which was cut on the following day after a struggle that cost the Americans 394 killed and wounded including a high proportion of officers. Meanwhile the two howitzers and single mortar had been positioned to fire on the citadel as the rest of Taylor’s army moved to attack the city from the east. The Battle of Monterrey lasted for three days as the Americans pushed into the streets of the city in a house-by-house advance. By 24 September the Mexicans had been driven into the area around the central plaza. When the mortar started to lob its bombs into this square Ampudia offered to surrender if his men were permitted to march out without hindrance and if an eight-week armistice was agreed. The Mexicans had lost 367 men, while the Americans had suffered 120 killed and 367 wounded in addition to an increasing number of sick.

Taylor thought Ampudia’s offer the best way to end the battle and save US lives, and the Mexicans marched out of the city. Another factor in Taylor’s decision was that a show of American magnanimity might help the peace process that had started when Polk had agreed to the return of General Antonio de Santa Anna from exile in Cuba on condition the loser in the War of Texan Independence used his influence in favour of peace.

Polk learned of Taylor’s armistice on 11 October and was furious that a Mexican army had been allowed to escape. He ordered the armistice to be cancelled, and on receipt of this news Taylor informed the Mexicans. Taylor then prepared to resume hostilities, on 13 November sending a 1,000-man force 70 miles (112.5 km) to the south-west for the capture of Saltillo. This was a strategically important city: it lay on the only road north from Mexico City able to take heavy wagons and artillery, and also commanded the routes west to Chihuahua and east to Victoria. This last was the capital of Tamaulipas, the province that also contained Tampico, Mexico’s second largest port on the Gulf of Mexico, which had been occupied by the US Navy on 15 November.

The importance of Saltillo to the Americans grew later in the the year, for on 5 December Wool’s force of 2,500 men arrived in Parras on the road between Saltillo and Chihuahua after a remarkable 600-mile (965-km) journey that had started in San Antonio on September 26 and proceeded via Presidio de Rio Grande and Monclova. During the early stages of his advance Wool had learned that the Mexicans had abandoned Chihuahua, his intended target, and had therefore shifted his route to the south with the intention of linking up with Taylor.

Taylor now prepared to use his combined force to prepare a strong defensive line between Parras in the west and Victoria in the east via Parras and Monterrey. No sooner had this plan been prepared that it was thrown into confusion when Taylor was told that most of his men would have to be detached for service in the fourth prong of the campaign, which had been added in Washington during mid-November.

Taylor had initially been ordered to advance 300 miles (485 km) to the south through the desert to San Luis Potosi as an initial step toward Mexico City, but had argued that such a move as unsound in purely military terms. Taylor instead recommended an advance on the Mexican capital from Vera Cruz, a move already suggested by Scott but at first refused by Polk because he feared the political strength that Scott might gain from such a success. The argument between Polk and Scott seriously delayed development of any plan, but Taylor’s endorsement of Scott’s strategy effectively forced Polk’s hand, and Scott was instructed to assume command of this new fourth offensive prong.

Leaving Washington on 24 November, Scott arrived in Camargo late in December and immediately detached from Taylor’s army 4,000 regulars and an equal number of volunteers. These were ordered to Tampico and the estuary of the Brazos river in central Texas. Scott then established his headquarters on Tampico on 18 February 1847.

The main offensive effort was thereby switched south, where a large-scale turning movement into central Mexico was to be made, and Taylor was ordered onto the defensive. He was instructed to evacuate Saltillo and concentrate round Monterrey with what was left of his army, fewer than 7,000 men. Of these only two dragoon squadrons and a small detachment of artillery were regulars.

Taylor was angry about this apparent waste of his efforts. On returning to Monterrey from Victoria, Taylor chose to consider Scott’s instructions as advice rather than orders. He therefore left small garrisons on Monterrey and Saltillo, and advanced 4,650 men to a point about 18 miles (29 km) to the south of Saltillo, and therefore nearer to San Luis Potosi. Santa Anna was determined to restore his reputation as Mexico’s ablest military leader, and thereby put the lie to newspaper suggestions that he had ‘sold out’ to the Americans. At San Luis Potosi an army of 20,000 Mexicans was being gathered. Scott’s plan had been leaked in an American newspaper, and the Mexican general decided that he had time to crush Taylor’s force before Scott’s army landed, a possibility that seemed even more attractive after Santa Anna received a copy of Scott’s orders to Taylor, taken from the body of an ambushed American courier. The Mexican army advanced from San Luis Potosi in the middle of winter in a gruelling march that cost it more than 4,000 men, and arrived about 35 miles (56.5 km) from Taylor’s position on 19 February.

Taylor had thought the march impossible and was accordingly taken by surprise. Nevertheless he decided to stand and fight. On the morning of 21 February scouts informed Taylor that Santa Anna’s army was moving forward, its cavalry swinging round to the east to cut the US line of retreat from the Hacienda Agua Nueva to Saltillo. Before the Mexicans could complete this move, Taylor pulled back to a point about eight miles (13 km) to the south of Saltillo, where at the Hacienda Buena Vista there was good defensive terrain. On the east, two mountain spurs came down to the road to the north and south of a plain divided by two deep gullies into what became known as the Northern, Central and Southern Plateaux. On the west was a mass of gullies backed by hills. Wool was charged with deploying the American main strength as Taylor departed to check the defences of Saltillo.

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