Mexican American War

Border Control: The Mexican-American War Redraws The Map

Mexican American War

Statesmen must be careful what they wish for.

In 1845, President James K Polk had been elected on a promise of carrying out America’s ‘manifest destiny’ by expanding US territory all the way to the Pacific.

At the time, the United States only stretched as far as the Midwest – the Oregon territory made up the south-western portion of British Canada, while the present-day south-western US lay in Mexican hands.

It would require a deal with Britain and a war with Mexico before the country’s modern contours were established.

Internal weakness dogged the Mexican side and ultimately handed victory to the US, but when Polk provoked the war by sending troops into Texas in March 1846, he didn’t realise he was setting up his own country for tremendous problems in the near future, and beyond.

the frontier
America's 'manifest destiny' to expand all the way to the Pacific as envisioned by artist Emanuel Leutze

The lands he and his supporters coveted and wrenched from Mexico’s grasp would trigger political upheaval and a national tragedy when they were incorporated into the United States. 

Dying of Cholera in 1849, Polk would not live to see the results his efforts, but the consequences of his actions while in office reverberate to this day. As Sam Haynes, author of ‘James A Polk and the Expansionist Impulse’, put it:

"Polk does more than any other chief executive to make the United States a hemispheric power, and that, in and of itself, is a remarkable accomplishment. But it’s the means by which that was achieved that I think have made many American historians rather uneasy, because he does bully a weaker nation into a war. This is a war of conquest. He may not have seen it that way, but most historians have judged him in that light."

Lines in the sand, and on the map

Long before Donald Trump proposed building a wall between the US and Mexico, the border was still being established. 

At its height, the Spanish Empire had run through much of South America - save Portuguese-held Brazil, Dutch-held Suriname and Guyana, and French Guiana – up through Central America, and through the Midwest to Canada.

But a series of wars, including in Mexico in 1821, led to the shattering of Spain’s empire on the continent.

President James Polk
Americans were highly literate by the standards of the time and the war would become a hot button issue in the press – people in the south and west were mostly behind the war whereas those in the northeast largely opposed it

In the years that followed, Mexico controlled much of Spain’s former northern territories that had not been siphoned off by Britain, France, and then US expansion.

This had included Texas, but a subsequent war with American settlers had seen this portion of Mexico break away.

These newcomers had been invited in by the Mexican government following Spanish withdrawal.

Texas was sparsely populated at the time, and hardy foreign migrants were needed to develop it economically. In exchange, they would be granted a certain amount of autonomy.

Life on the frontier was tough, and settlers were liable to be attacked by Indians while they contended with the harsh environmental conditions. 

Although it recreated life in Montana in the 1880s, ‘Frontier House’ still gives a window into what was endured by those throughout the unsettled west.

One striking statistic is that 60 percent of those who went to the frontier did not survive the five years required to officially claim the land they had relocated to. This kept life expectancy in the area at around 40 years of age.

So the homesteaders in Texas could reasonably argue that they had kept up their end of the bargain with Mexico by simply surviving. Thus, when a new Mexican government sought to alter the terms of their deal, and curtail the Texans’ (or Texians’) autonomy, this eventually provoked war. 

Mexican American War
President Polk (left) and a map of Texas showing the disputed area as American "Claimed Territory" (right; image: Ch1902)

The Texans won and their territory was later absorbed into the US. However, the problem for President Polk was that the Mexican government never accepted the terms of the treaty signed by captured generalissimo Santa Anna at the end of hostilities. 

The result was that Mexico saw Texas’ boundary with them as being set at the Nueces River, while the American government saw the border as being further south at the Rio Grande.

It was Polk’s determination to assert the American interpretation of the border by force that sparked the conflict. Sending troops into the disputed territory in March 1846, Mexico declared war on April 23. Two days later the first shots of the conflict would be fired.

A profile of two nations at war

In his account of the conflict, Douglas V Meed describes the US as "a society based on a democracy founded on British common law, the European Enlightenment, and a secular government". ("In God We Trust" was not actually adopted as the national motto until 1956, before which it had been "E pluibus unum": ‘Out of many, one’). 

Paradoxically, this vigorous, growing democracy of 20 million permitted slavery.

Soldiers of the Mexican American War Osprey
Soldiers of the conflict: 1: A private in the New York Regiment; 2. A Texas Ranger; 3. A Mexican Grenadier Guard (image from ‘The Mexican American War 1846 – 48’ by Philip Katcher © Osprey Publishing, part of Bloomsbury Publishing)

By contrast, Mexico’s seven million people were traditional, religious, free of slavery but plagued by huge bifurcation: "It was a land divided by race, caste, and a massive economic gulf between rich landowners… and the mass of landless peasants".

Still, despite being racked by internal division, many at the top of society were confident they could smash the ‘impudent’ Americans. After all, the population figures were reversed militarily: At the start of the war, Mexico’s army was 20,000 strong and pitted against a mere 7,000 American regular soldiers dispersed throughout the west.

As it happens, most of the American soldiers were not American at all. Two-thirds of them were foreign born, largely Irish, but also German and British, and many had joined up to get the three-square-meals-a-day and $7-a-month package that came with service. These men were well drilled and led by an experienced officer corps.

By contrast, the volunteers who swelled the ranks when the war commenced were largely headstrong American-born southerners or westerners in their late teens or early twenties. According to Meed:

"Some volunteer regiments had their fighting record marred by lack of discipline, rowdy behaviour, looting, and, not uncommonly, crimes against the Mexican civilian population. The Texans were the worst." 

Tortilleras_Nebel 1836 women grinding corn for tortillas
Mexican women are shown in this picture grinding corn to make tortillas

While they may have been outnumbered, the average American soldier was considerably better nourished than his Mexican counterpart. 

As largely landless peasants, they were fed on a diet of Indian corn, rice, and beans and averaged only 5'2" in height (although American soldiers later reported being surprised by how fit and athletic their enemies were, despite them being small in stature). American farmers, meanwhile, had grown up on fresh meat, wheat bread and vegetables and were considerably bigger (American soldiers 15 years later would average 5'8").

Mexicans were largely poor conscripts doing six-year tours (all bachelors and married men without children were theoretically required to serve; in practice, many middle and upper-class men used political connections to get out of it). 

This did not exactly instil much sense of solidarity in the Mexican army, and while breakdowns in discipline often manifested as combativeness in American volunteers, for Mexicans it showed up in high desertion rates. Malnutrition and equipment and clothing shortages (many peasant soldiers marched in sandals, or even barefoot) only made this worse.

In terms of weaponry, American troops carried a 10-lbs flintlock musket with an enormous .68-inch lead ball for ammunition (by way of contrast, today’s most powerful handguns fire rounds that are .44 or .45 of an inch in width). Some weapons had been adapted to use the new-and-improved percussion caps.

Effective range was about 200 yards, but sights were set up to 120, and soldiers would normally fire three aimed shots a minute. At close range, they could pelt the enemy with the truly lethal 'buck and ball' which was composed of one regular-sized shot and three small ones.

Abraham Lincoln as a congressman - he opposed the war, accusing Polk of lusting after "military glory—that attractive rainbow, that rises in showers of blood"

Rifles were effective up to 400 yards and issued to selective units, such as the Mounted Rifles Regiment and the 1st Mississippi Volunteers, but the longer barrels made them tougher to reload (ram rods had to push rounds all the way down the barrel before it could be fired). This reduced the effective rate of fire to one per minute.

By contrast, cavalry were issued with carbines (usually with percussion caps) and single shot pistols, although the Texas Rangers carried one or two Colt five-shot repeating pistols instead.

Mexican soldiers were relatively well equipped (although the US naval blockade of their ports would hamper them later in the war). They bore British Brown Bess muskets which fired a .75 inch lead shot to about 100 yards, while men with Baker flintlock rifles (also British-made) could fire their .62 inch rounds up to 200 yards.

Unfortunately, poor training often reduced the accuracy and rate of fire of these men. This problem was exacerbated by poor quality gunpowder, forcing soldiers to use more of it. The extra kick this produced further impeded accurate shooting.

Cavalry, however, were an elite corps, equipped, like the Americans, with carbines, single-shot flintlock pistols and swords. They also had lances, and sometimes lassos. 

Downtime for Mexican soldiers differed depending on rank. Officers engaged in political discussions and horse racing; for the men, songs and cards around the campfire were the norm, with an occasional cockfight thrown in. Many of these men were far from home and suffered homesickness, much like the Americans, whom they would be meeting in battle soon.

Palo Alto: Flying artillery carries the day

Initial fighting took the form of skirmishing, with the Mexicans first opening fire on April 25, 1846, on the American soldiers who had been sent into the disputed territory in Texas.

But once the armies engaged each other properly, the first major battle set the tone for much of the rest of the war.

The Battle of Palo Alto

On May 8, both sides met on the coastal plain of Palo Alto, near what is now Brownsville, Texas.

The Americans were considerably outnumbered. According to KJ Bauer’s ‘The Mexican-American War 1846 -1848’, Major General Zachary Taylor had a mere 2,288 troops to General Mariano Arista’s 3,709 men.

But Taylor had an ace up his sleeve, and that was a young West Point graduate named Major Samuel Ringgold. 

Setting up his heavier 18-pounder guns in the centre of the field, he bolstered this with lighter artillery on the left, and plenty of infantry in the centre and on both sides. Meanwhile, supporting the infantry on the right flank was Major Ringgold and his ‘Flying Artillery’.

These were specialist lightweight (880 lbs), horse-drawn, 6-pounder guns that could be towed and swung into position very quickly, even on difficult terrain. They also had a range of 1,500 yards, which considerably outclassed the average musket, and over which they could fire solid shot, explosive shells, or a kind of grapeshot that sprayed the enemy with smaller balls.

With 12 of these guns, the Americans had the potential to devastate the enemy that day. 

In the early afternoon, the Mexicans began the battle by firing their own artillery, but their solid shot, flying over a great distance, plonked down and bounced over the terrain harmlessly.

The Americans, meanwhile, had better-trained gunners and were able to fire eight rounds of artillery for every one of the enemy’s. 

When the elite Mexican horse-drawn lancers charged them, Ringgold’s explosive shells were soon obliterating their ranks. Likewise, wherever the enemy’s infantry tried to advance, Ringgold’s guns were promptly pulled into a position from where they could obliterate them at close range.

As it happens, Ringgold himself was killed when one of the few cannon balls fired accurately by the enemy hit him in the leg.

Still, if the death of the young major was a tragedy, it was nothing next to the anguish of the wounded Mexican soldiers.

They were left behind screaming when General Arista withdrew and they were consumed by fires started on the prairie grass by the constant firing.

Mexican casualties were estimated at between 400 and 700. There were 12 killed and 40 wounded in the American ranks.

It was a similar story the following day on May 9, when Taylor’s forces caught up with Arista’s men who were arrayed in what they thought was an effective defensive position.

Resaca de la Palma, Texas, 9 May 1846
The Battle of Resaca de la Palma, which took place on May 9, 1846

Several hours later, after brutal charges with close-combat characterised by flashing sabres and men being beaten by musket butts, 1,200 more Mexicans were dead or wounded, 100 had been captured, and 2,000 more deserted. Vultures and wolves fed on the unburied bodies for days.

Although the Americans had got off with a comparatively light 34 dead and 113 wounded, ‘American blood having been spilt on American soil’ (which this part of Texas was considered to be by the US) now prompted Congress to officially declare war and raise volunteers and cash for the effort.

A glorious journey

One regiment that answered the call was the Missouri Volunteers.

Led by the 6'6" 240-lbs lawyer, Alexander W Doniphan, the 1st Regiment of Missouri Mounted Volunteers would distinguish itself about as much in this war as the ‘Rough Riders’ later would in the Spanish-American war.

Taking a truly epic circuit out from their home state and down into Mexico, they fought battles, struggled through desert, and rescued ‘fair maidens’ from Indians during their one year of service.  

From a military standpoint, the most interesting aspect of Doniphan’s journey is his decision to not attack enemy soldiers spanning the road in front of the capital of the state of Chihuahua.

Mexican-American War
A map showing the progress of the Missouri Volunteers during their year of service (image from ‘The Mexican American War 1846 – 48’ by Douglas V Meed © Osprey Publishing, part of Bloomsbury Publishing)

Outnumbered three-to-one, Doniphan instead outflanked the enemy, moving his 1,000-strong battalion and guns up a cliff until he was in position to enfilade them will full force.

Meed describes what happened next:

“Doniphan dismounted some of his men and then charged the now disorganized foe. Gun butts smashed and Bowie knives slashed in close-quarter fighting until the Mexicans retreated in disorder. Doniphan reported that he had captured 10 guns and 10 wagons, killed 300, and wounded another 300. His losses were two killed and a few slightly wounded.”

After covering more than 5,000 miles, the men returned home a year after they had started out. They were welcomed back as heroes. (Volunteer units were only required to serve for a year, and so many went home before hostilities were over. As the war progressed, enlistment terms were amended to require men to stay until hostilities ended).

The war escalates in the north

Reeling from their defeats, the Mexicans would soon be dealing with a rebellion by the tiny community of American settlers in California as well.

It was clear they needed a new leader.

This would prompt the return of a familiar face: Santa Anna, the ‘Napoleon of the West’ (a nickname he gave himself). He had led Mexico during the Texas War of Independence and would be president of Mexico several times over the course of his life. He had been sent into exile in Cuba by his own countrymen, but now they wanted him back.

Convincing the US President that he would sign a peace treaty upon his return, Polk consented to let him through the US naval blockade.

Mexican-American War
Santa Anna, who would lead the Mexican Army

Once in Mexico City, Santa Anna reneged on his promise and seized power. He rallied his army and they prepared to meet General Taylor.

In the meantime, the age-old problem of armies at war was plaguing the Americans – that of stretched supply lines. 

Taylor’s army was getting more ragged as they advanced further south, their uniforms and shoes worn out as the campaign continued. Rations were also blighted by microbes, often unusable by the time they’d made it all the way down from New Orleans. One test used for rancid meat was to fling it against a camp wall and see if it stuck (it wasn’t consumed if it did).

Fortunately, the meagre rations could be supplemented by tamales, enchiladas, tacos and tortillas bought from locals. 

Men had kept their morale up by socialising around the campfire, even if that did often involve moaning about army food. Card games and conversations about girls left at home were commonplace. Popular sing-alongs included ‘Home Sweet Home’ and ‘The Girl I Left Behind Me’. 

Other than bartering for food, other contacts with the locals were not quite as cordial. When near a town, taverns and brothels were the biggest draws, leading to fist fights after copious amounts of alcohol consumption, and gonorrhoea and syphilis following other activities. This only added to the non-combat related casualties already caused by diseases (these figures would outstrip combat deaths and injuries not only in this war but for all wars throughout the 19th century).

Many officers stayed out of such things, preferring to have literary readings, comical play productions, or to hold debates on contemporary issues. 

But disease and poor rations aside, Taylor’s army held together and by September of 1846, the Americans were approaching Monterey. 

10,000 Mexican troops had fortified the city approaches, but Taylor’s men split up and soon broke through.

Battle of Monterry
The Battle of Monterey (image from ‘The Mexican American War 1846 – 48’ by Douglas V Meed © Osprey Publishing, part of Bloomsbury Publishing)

Meed notes that some historians believe the fighting that next unfolded within the city may have been informed by the experience of Texans, who’d fought against the Mexicans in urban environments before.

Whatever the source of their training, the American troops were prepared to smash through walls with pickaxes, and to blow holes in them with artillery before flooding in to slay any survivors.

Riflemen would perch on the roof to snipe at anyone in adjoining streets or houses, and in this manner, the city was eventually cleared building by building, house by house.

This was not a foregone conclusion though. During this stage of the battle, ammunition started to run perilously low.

But a brave young officer offered to ride through the sniper-packed streets and bring in more. He did so, heroically hanging off one side of his mount to avoid being picked off before then galloping back into town with the necessary ammunition wagon.

The city was soon in Taylor’s hands and he signed a ceasefire, which enraged President Polk when he heard, believing it was merely a way for Santa Anna to stall while he regrouped.

He sent Major General Winfield Scott to replace Taylor.

Zachery Taylor is said to have been down-to-earth, approachable, and to have dressed rather scruffily – to the point that those not familiar with him would not have known he was in command until informed so. 

Winfield Scott, by contrast, is said to have been proud, possibly to the point of being somewhat haughty, and he took great pride in his appearance, so much so that he was known as ‘Old Fuss and Feathers’. Egotistical and short tempered, he had made a number of political and military enemies.

Mexican-American War
Major General Zachary Taylor (left) and Major General Winfield Scott (right)

Taylor and Scott also differed politically. Taylor was a Whig (a forerunner to the Republican Party) – in fact, he was a prime candidate for the party’s nomination in the 1848 election, which would have seen him run against Polk. He suspected that Scott had been sent to replace him by President Polk, a Democrat, to trash his reputation and frustrate his political ambitions.

Refusing to resign, American forces were split as after Scott arrived and led the main force further south while Taylor was left to guard Monterey.

Santa Anna’s scouts had been watching, and when they relayed this information to their commander he knew it was time to isolate and strike Taylor’s smaller force. Polk had been right – Napoleon of the West had used the ceasefire to gather his forces, and now he would lead them north to smash Taylor’s smaller force.

Fortunately for Taylor, a Texas Ranger captain had sneaked close to the enemy and gathered important information about the size of the force coming the Americans’ way.

Mexican-American War
The Battle of Buena Vista (image from ‘The Mexican American War 1846 – 48’ by Douglas V Meed © Osprey Publishing, part of Bloomsbury Publishing)

General Taylor complained about the Rangers, remarking at one point that "there is scarcely a crime that has not been reported to me as committed by them". Known for adopting Comanche Indian tactics and said to be related to many who had died at the Alamo ten years before, the Texas Rangers were known by the enemy as Los Diablos Tejanos (‘Texas devils’). 

Indeed, before the battle at Monterey, they’d climbed a fortified position under the cover of darkness and a rainstorm and savagely murdered the Mexican garrison with pistols and bowie knives.

But Taylor needed them, and they had again proved their worth. It was now February 22, 1847 and the Battle of Buena Vista was about to commence. 

Battle of Monterrey
The Battle of Monterrey - American troops approach the city which is shown in the background
Battle_of_Buena_Vista_Nebel extra
The Battle of Buena Vista

The intelligence related by the Rangers had allowed Taylor to position his 4,700 men in the best place in time to meet the onslaught of more than 15,000 Mexicans coming at him. American artillery was again used to lethal effect, and by nightfall, Santa Anna had sustained 3,500 casualties to Taylor’s 650.

He could not press on – he needed his army intact to take on General Scott. Political turmoil back in Mexico City also forced his hand, and so Santa Anna retired to crush this dissent before intercepting the bulk of the American forces further south.

Mexico's war heads south

Old Fuss and Feathers came ashore with 12,000 men on March 9, 1847, near Vera Cruz, an important Mexican seaport and an important stepping stone in getting to the capital. His men had been transported via an impressive armada of 100 ships, but such overwhelming force was necessary – Scott knew he had to take Vera Cruz before April brought yellow fever with it.

Fortunately, this deed was accomplished quickly under the watchful eye of a talented engineering captain who reconnoitred the fortified city then brought naval guns ashore to bombard it for five days. It soon fell.

The bombardment of Veracruz
The bombardment of Vera Cruz

Now Scott had the foothold he needed and he pressed inland.

Santa Anna had set up his forces, and particularly his artillery, to catch the Americans in a crossfire as they walked through a valley, but the same engineer captain came to Scott’s rescue a second time. 

Through careful reconnaissance, he found another route and, after launching a feint attack on Santa Anna’s main front, Scott led the bulk of his force around and ambushed the Mexicans from behind. 

Mass disarray broke out and 3,000 Mexicans fell into American hands while hundreds more ended up as casualties and Santa Anna was forced to flee.

But Scott’s progress was checked by both the onset of disease within his ranks, and the depletion of those ranks by the ending of the one-year service term agreed to by the initial wave of volunteers. Refusing to see things through, the volunteers insisted it was their right to go home and overnight Scott’s force was cut to less than 7,000 men.

Fortunately, Washington had seen to it that Scott be reinforced and another 7,000 troops soon arrived, along with the diplomat Nicolas P Trist, who President Polk had sent to negotiate the peace treaty he assumed would soon be forced on Santa Anna.

But that would be easier said than done. 

While Scott had been waiting for reinforcements, ‘Napoleon of the West’ had crushed more opposition at home and had now built his army up to between 25,000 and 30,000 troops.

Closing in on the capital

Undaunted by a defending force that considerably outnumbered his 10,000 men (a force already depleted by disease), Scott continued to Mexico City.

Again, the engineers came into their own, figuring out and preparing the best routes for Scott’s men. Santa Anna was soon against the wall again, and a ceasefire was agreed, the provisions of which would be a prisoner exchange, no reinforcing of either side, and the ability of the Americans to get food.

None of these played out in Scott’s favour. To start with, the Americans had taken many more prisoners than Santa Anna, who also went on to waive the second provision and raise more troops anyway. Lastly, when the Americans entered Mexico City to buy food they were attacked by angry Mexican soldiers and citizens and had to retreat. Scott ended the armistice.

It was now September 1847 and the end of the war was in sight. Scott just needed to take Chapultepec castle, a central part of Mexico City’s defences.

During the course of the war, there had been many changes of fortune for both sides. 

Mexican-American War
Zocalo Cathedral in Mexico City today (image: Jeff Kramer)

Santa Anna was despised and many Mexicans, including some in government, cooperated with the Americans. Some Mexican women even served as ‘soldaderas’ for the Americans, as others did for their own soldiers, functioning as cooks, washerwomen, nurses and sex partners.

Other Mexicans happily gave Scott useful information on Santa Anna and his troops.

Meanwhile, the Americans had ‘turncoats’ of their own. 

The San Patricios were a group of roughly 200 mostly Irish deserters who, disillusioned with the war and embittered by discrimination within the Protestant-dominated US Army, had opted to fight with their fellow Catholics on the Mexican side.

They were experienced artillerymen who had served with the British, and they put their expertise to deadly effect, especially at Chapultepec, where they suffered 60 percent casualties.

Gen.John A. Quitman make a move on Mexico City in Mexican–American War Marines
American marines enter Mexico City

At first, the attack did not go well for the Americans. They had planned to scale and then pour over the walls of the castle, but after rushing up the hill they had to wait for scaling ladders a quartermaster had failed to make available.

When they arrived, the men rushed up them and the attack turned into the Alamo in reverse, with the besieged Mexicans being overrun this time by the Americans.

Meed describes what happened next:

"As the Americans advanced through the castle, there… (were) 50 teenaged military school cadets, some as young as 13, who refused to retreat before the swarming Americans. When the surging Americans rushed at one 13-year-old cadet, he refused to throw down his musket and surrender. He was quickly bayoneted. Three other cadets, fighting like demons, were killed in the palace corridors."

Another one of the cadets took his country’s flag and dashed along the battlements with it, refusing to let it be captured. He was riddled with musket rounds and fell to the rocks below, wrapped in the flag he had tried to save. (This is apparently a story retold to Mexican schoolchildren today, while all the ‘Ninas Heroicos’ have a monument at the foot of Chapultepec today).

Los Ninos Heroes and Santa Anna
Santa Anna's gravestone (left; image: Jonas zacarias) and the monument to the Ninos Heroes (right; image: Leandro Neumann Ciuffo)

As noted, the San Patricios also fought largely to the bitter end. Those that were captured were executed, some by being dragged over the castle walls with ropes attached to a large American flag around their necks. (The flag was attached to mules on the other end that were swatted to make them leap forward and haul the flag).

Santa Anna fled, waiting to be besieged elsewhere, and skirmishing erupted throughout the city as the last gasps of resistance to the Americans had to be overcome.

But a new government came to power and relieved Santa Anna of his command. He would be president for one last time in the 1850s (he’d been president 10 times before that) before being exiled again. Eventually, though, he would return and die in Mexico at the very respectable age of 82, receiving full military honours at his funeral.

Politics by other means

The Treaty of Guadalupe Hidalgo – that was the real point of the war.

While the Texas War of Independence had been borne out of genuine grievances, the Mexican-American War is generally regarded as a land-grab. 

U.S. Army occupation of Mexico City in 1847 Mexican American war
The US Army occupies Mexico City - Zocalo Cathedral is visible in the background

Trist would negotiate the sale of Mexico’s northern territories to the tune of $15 million. Polk had offered to buy them before the war for $30 million. The pay cut was presumably Mexico’s punishment for refusing.

Prosecuting the war had cost the Americans $100 million dollars - $3 billion today when adjusted for inflation.

Historian Brian DeLay has said that historians have wondered why so little attention is paid to the Mexican-American War in the study of US history. He says:

“I think the... reason is that the... war does not fit well with our idea of what American history is really all about. We like to structure our history around important wars, particular wars – the Revolutionary War, the Civil War, and World War II. And in each one of these cases we remember these as conflicts where we were attacked by an aggressor, this aggressor had designs on something really fundamental to who we were – our liberties, our freedoms – and through enormous personal sacrifice and heroism, we overcame enormous odds and drove back this threat. And the Mexican War doesn’t fit this pattern… We want to believe that we’re still the kind of virtuous people that wouldn’t fight an aggressive war this way, but we certainly are happy with all the results of that war.”

Happy now, perhaps, with the extra territory it brought into the United States.

1848 US Mexico new borders
New US territories and Mexico's new border following the war (image from ‘The Mexican American War 1846 – 48’ by Douglas V Meed © Osprey Publishing, part of Bloomsbury Publishing)

But there were grave consequences to the war for Americans in its aftermath.

At first, the Americans struck gold with their new territories – literally. The California gold rush started when gold was discovered there after the war. Its worth far outstripped what the US had paid for the war, allowing them to recoup what they had spent to wage it.

But the American ship of state was unsteady and heading into perilous waters. Northeasterners despised the war, seeing it as a war of aggression, but falsely believing the new territories could become slave states. (The climate in the west wasn’t suitable for crops like cotton, for which slave labour was used at the time).

A ferocious dispute opened up in the Congress as abolitionists fought to ensure that slavery would not spread, fearing an imbalance of slave and free states in the newly configured union.

There would be an imbalance, but one going the other way. When California, then Minnesota, then Oregon, were admitted into the US as free states, the pro-slavery south knew they would now be outvoted in both chambers of the Congress (the House and Senate).

When the Mexican-American War had started, Mexico had bet on the anti-slave north seceding from the US and going to war with the land-grabbing southern and western states. Now it was the south that was beginning to eye succession favourably. 

It would be the election of the anti-slavery president Abraham Lincoln that would finally trigger this, and when the American Civil War started in 1861, Old Fuss and Feathers, Winfield Scott, would be by his side. He hatched the ‘Anaconda Plan’ to encircle and economically strangle the south.

1861 - 1865
The Anaconda Plan

But one man who would not be with Lincoln would be the intellectually brilliant engineer who had helped General Winfield Scott find the best route to so many of his victories. His name was Robert E Lee, and he would lead the army of the Confederate States of America during the civil war. 

Meanwhile, the dashing young officer who had risked life and limb riding through the sniper-infested streets of Monterey to bring ammunition to Taylor’s forces would also play a major role in the future civil war. His name was Ulysses S Grant, and he would eventually lead the Union forces of the north that would finally bring Lee’s army to heel in 1865.

In fact, many soldiers of the Mexican-American War would find themselves on opposite sides during the American Civil War as the political consequences of the Treaty of Guadalupe Hidalgo unfolded and the US tore itself apart.

For more information, read ‘The Mexican War 1846 – 1848’ by Douglas V Meed, or Philip Katcher’s ‘The Mexican-American War 1846 – 1848’ in the Men-at-Arms series to learn more about the fighting men and their uniforms in that conflict. Visit Osprey Publishing for more military history.

US Civil War
Ulysses S Grant (left) would lead the Union Army against Robert E Lee (right) who commanded the Confederate Army during the American Civil War