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19th Century Articles
The French vs. German Strategy of Warfare 1871
Invention of Counterinsurgency
Alfred Thayer Mahan: Advocate for Seapower
Americans in the Boer War
Marching to Timbuktu
Charge of the Polish Light Horse at Somosierra
The War between Norway and Sweden 1808
Gonzales: Crucible of Texas Revolution
Sheridan's Southern Plains Campaign
Milvern Harrell: Dawson Massacre
Mexican American War
Giuseppe Garibaldi
Solferino: Slaughter and Rebirth
Battle of Lundy's Lane
Battle of Paris
Stephen Douglas and Popular Sovereignty
Napoleon's Campaign Of 1809
Capture of USS President
The Fenian Raids
Military History of War of 1812
Austerlitz: Napoleon Makes His Own Luck
The Failures at Spion Kop
Combatants in Black Hawk War
Tunisian Army in Crimean War
Giuseppe Garibaldi
The Mitrailleuse
The Grande Armee of 1812 in Russia
The French Campaign of 1859
The French Intervention in Mexico
The Master's Misstep
Trafalgar Remembered
Rorke's Drift

Phillip Muskett Articles
Mexican American War
Confederate Railroad

Recommended Reading

Dueling Eagles: Reinterpreting the U. S.-Mexican War, 1846-1848

So Far from God: The U.S. War With Mexico, 1846-1848

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A Brief History of the Mexican-American War
A Brief History of the Mexican-American War 
by Phillip Muskett

The United States has fought many wars in its two centuries of existence. These wars were fought for state’s rights or against fascism and communism. The Mexican American War of 1846 was fought for land and sixteen years later this war nearly destroyed the Union. The American victory in the Mexican War added over 500,000 square miles of territory to the United States. This war, the first America fought on foreign soil, was another step toward completing the United States “Manifest Destiny.”

Politics played a large part in this war; the Democrats wanted the new territory to expand slavery, while the Whigs feared the expansion of slavery. The two generals that led the U.S. Army were Whigs and the President of the United States was a Democrat, this caused stress that worked against the American forces in Mexico. President James K. Polk desired to accept the Republic of Texas into the Union so their citizens could enjoy the blessings of liberty.[1] The two Generals had their own eyes on the White House in 1850.

Mexico was in political turmoil during the era before the war. Antonio de Lopez Santa Anna was President or Dictator of Mexico numerous times before finally being banished to Cuba. Santa Anna came back to Mexico after the opening battles of the war and immediately mobilized a large army and began moving north to occupy Texas, ensuring it remained in the Mexican Republic. Santa Anna believed strongly in Mexico’s territorial integrity and it was the most important part of his reason for engaging in the war.[2] Texas annexation was the United States’ main goal of the war with Mexico and Mexico’s goal was to keep its territory. With these strong wills, the war was inevitable.

James K. Polk had won the Presidential election of 1844 on a plank to annex Texas into the Union. He stated in his inaugural address, “I regard the question of annexation as belonging exclusively to the United States and Texas.”[3] On March 1, 1845 the annexation of Texas was ratified by the United States Congress.[4] This claim outraged Mexico, and upon receiving word of the passage of the measure, the Mexican Foreign Minister of Relations, Luis G. Cuevas, considered all relations between the two countries severed.[5] President Polk was not a man to back down from a challenge and was willing to do whatever it took to get the territory that allowed the United States to claim its “Manifest Destiny”.

President Polk was very methodical and paid meticulous attention to detail; therefore trusted no one. He wrote to a friend, “I intend to be, myself, President of the United States.[6] This statement describes a man who would choose men to do his and only his bidding. Polk would go so far as to try and supplant the senior officers in the army for someone loyal to him. To do this he planned to instate a loyal Democratic Senator, Thomas Hart Benton who was a trusted Polk confidante, to the position of Lieutenant General. Benton would supplant Generals Winfield Scott and Zachary Taylor, who were Whigs, and whom Polk did not trust to prosecute the war, as he planned. Polk would only serve one term as President of the United States; he would die four months after leaving office. Perhaps the release of all the self imposed stress killed him?

General Winfield Scott was the senior officer in the United States Army at the outbreak of the Mexican War. He served in the United States Army from the War of 1812 until the American Civil War in 1861. During the Mexican War, President Polk feared General Scott as a political adversary did not favor him. General Scott disapproved of the strategy that President Polk used to prosecute the war, so he refused to take the field with the army on the Texas border.[7] This added to the mistrust between the two men. President Polk felt compelled to find another General to lead his army.

When General Scott refused to take the field and command the army at Corpus Christi, President Polk turned to General Zachary Taylor. This was not a popular choice for the President, as General Taylor was also a Whig. (Taylor would later become actively involved in the politics of the time, and replace President Polk as President of the United States.) As the war progressed Generals Taylor and Scott’s relationship also soured. In a letter dated September 27, 1847, Taylor described Scott as “stooping to anything however low and contemptible as any man in the nation, to obtain power or place…”[8] While Scott thought that Taylor was “quite ignorant for his rank and quite bigoted in his ignorance.”[9] General Taylor saw General Scott as a meddler; Taylor felt that Scott took Taylor’s army away from him, so Scott may win glory for himself.

General Taylor performed brilliantly during the early months of the war; winning victories on the battlefield that secured Texas and northern Mexico. Taylor would not stay in President Polk’s favor after the autumn of 1846, when he allowed the Mexican army to escape after the battle of Monterrey.[10] Taylor would use this time while Scott was winning the war, to win the White House.

Antonio de Lopez Santa Anna served as President (or Emperor) of Mexico numerous times. After the Mexican defeat at the battle of San Jacinto, Santa Anna returned home, deposed of power and then returned to power upon the failure of the interim government, where he held the office from 1841-1844. His Presidency failed again, and the Mexican government exiled him to Cuba. He was only exiled a short period before President of the United States, James K. Polk, allowed him to return to Mexico.[11] Santa Anna had promised to try to end the war before it occurred. President Polk mistakenly believed that Santa Anna, who raided Texas settlements for numerous years, would secure peace. Santa Anna did not end the war, but instead prolonged it.[12] He would not accept defeat, even after losing every battle he fought against the Americans. When Mexico City fell to the American army, Santa Anna planned to continue fighting, but his popularity had waned and no one would support his efforts. Santa Anna spent the rest of his life attempting to justify his actions as President and the Commander of all of Mexico’s armies.

The territory that was the goal of the war was Texas. Texas became an independent Republic following the Battle of San Jacinto on April 21, 1836. This battle had been a decisive defeat for the Mexican army, but Mexico refused to recognize Texas as an independent nation. The Mexicans felt, when Antonio de Lopez Santa Anna signed the treaty that ended that war, that the Americans coerced him into it. The Mexican government, even Santa Anna himself, would not officially recognize the treaty. The Mexican government recognized the original treaty that the United States signed with Spain to annex Florida, which moved the Spanish border to the Sabine River, not the Rio Grande. Mexico invaded Texas numerous times during the years between the Texas Rebellion of 1836 and the war with the United States. In March of 1842, Santa Anna ordered a force of seven hundred men, under General Rafael Vazquez, to occupy San Antonio. They captured San Antonio for two days, before returning to Mexico with their plunder.[13] This attack, and others like it, created a desire from many Texans to join the United States, if only for protection.

Mexico was not the only nation against Texas annexation; England was against it as well. England feared the United States would threaten their position in the world, if the nation reached from the Atlantic to the Pacific Ocean. There had been accusations of English activities to subvert the annexation, but it was not until March of 1845 that these activities were exposed. A British agent, Charles Elliot, worked out a deal with the Republic of Texas President, Anson Jones, to wait three months for Elliot to work out a deal with Mexico.[14] Elliot hoped to convince Mexico to recognize Texas’ independence, so England could block American expansion. Elliot performed this mission incognito.[15] The Americans clamored for action when Elliot’s cover was blown in Mexico City. Elliot’s mission ended in failure and England had no further influence on the annexation of Texas.

On March 1, 1845, John Tyler, the outgoing President of the United States officially offered Texas annexation into the United States; this was the last act of his presidency. The Congress of the United States approved this measure, with only three days left in Tyler’s administration. This enraged the Mexican government, who immediately cut all diplomatic ties with the United States. The antagonists began to prepare for war.

Brigadier General Zachary Taylor received orders to begin gathering his army near the Texas border at Fort Jessup, Louisiana. The majority of the regular army would begin arriving there. All the troops in the west, northwest and the Atlantic coast were sent to General Taylor.[16] Professional soldiers, also known as regulars, made up General Taylor’s army. It was against regulations to call volunteer soldiers into service to invade another country; only after the declaration of war could volunteers serve. The nation relied on the volunteers, not a standing army, to defend the country. Americans believed that the volunteer soldier was the sole hope for defending the country.[17] The regular army was there to protect the country’s interest, until the volunteers arrived. The regular soldiers were usually left out of the glory and fame once the volunteers arrived.

During July of 1845, General Taylor received orders to move his army to Corpus Christi. Taylor sent his cavalry and artillery overland to Corpus Christi and sent the infantry by ship to perform an amphibious landing. It took days to get all the men ashore due to the shortage of shallow draft boats. The new Army of Occupation had plenty of time; they did not leave Corpus Christi until March 8, 1846. While occupying the city the army drilled and organized. Future Major General, William B. Franklin wrote “the little army became ‘well-nigh’ perfect in these qualities.”[18] When the army did begin to move, Lt. G. G. Meade described it as a “hurry-scurry”.[19]

General Taylor left Corpus Christi and moved his army south toward Matamoros; the army could provoke a fight there. Future President U.S. Grant wrote about this later, when he stated, “…the presence of United States troops on the edge of the disputed territory furthest from the Mexican settlements was not sufficient to provoke hostilities. We were sent to provoke a fight, but it was essential that Mexico should commence it.”[20] The armies glared at each other for almost a month before any action occurred. Mexican General Mariano Arista immediately began ordering raiding parties into the disputed territory. The situation changed on April 23, 1846, when the Mexican army began sending troops across the Rio Grande; they captured a patrol of United States soldiers’.[21]  The casus beli, which President Polk needed to declare war, had occurred. The United States Congress on May 12, 1846 approved President Polk’s request for war; therefore opening hostilities with Mexico.

With war officially declared, General Taylor crossed the Rio Grande and moved into Mexico. His objective was the Mexican army that had formed for battle near Palo Alto. This battle, fought on May 8, 1846, was indecisive, but the Mexicans retreated, abandoning the battlefield. Mexican General Arista moved to a stronger position near Resaca de la Palma. This battle, fought on May 9, 1846, was a decisive victory for the Americans, they routed the Mexican army. None of the volunteers participated in these victories. The United States Army regulars had their victories and glories, but the volunteers would dominate the rest of the war.

Each state answered the call for volunteers with overwhelming enthusiasm, and each state met its quota of men. In fact, the state organizations turned many volunteers away. These men came back a year later when a second call for volunteers was issued by the government. When the volunteers arrived in Mexico, they expected glory and fame but instead they found disease and death. The army camp at Camargo was a death camp, where one in every eight men who camped there died.[22] Lt. George McClellan wrote about the volunteers’ conditions, in his diary, “they literally die like dogs.”[23]

General Taylor began moving his army toward the northern Mexican city of Monterrey and away from the death camp at Camargo. The last troops left Camargo on September 6, 1846. The Mexican army had changed commanders again and its new commander was familiar. General Pedro de Ampudia was back in command and he was hoping to begin offensive operations to defeat Taylor’s smaller army. In the first five months of the war, the Mexican army had four different commanders of its northern army.[24]

The armies fought the climatic battle of Monterrey over September 20 - 24, 1846. When General Taylor arrived at Monterrey, he split his forces; sending one column around the town to take the dominating high ground. The main column moved into position to pin the Mexican army down, not allowing them to reinforce the heights. The initial attacks by the American forces forced the Mexicans back into town, who barricaded the streets and fought bitterly. This battle was America’s first experience with house-to-house fighting. Taylor wrote, “…streets were barricaded in the houses which were themselves each a fortification all built of stone with very thick walls with loop holes for small arms…”[25] The casualties favored the Mexicans, who lost around 400 men, compared to approximately 500 Americans[26]. The American army was much smaller than the Mexican army and could not afford these losses. The Mexican army surrendered on September 24, 1846 after Taylor’s forces occupied the high ground and began to bombard the town. General Taylor unwisely consented to an eight-week armistice and would later write a letter explaining why he allowed the armistice. First, he understood that both governments were trying to solve the issue diplomatically, therefore the armistice would last the eight weeks or if word came from either government. Secondly, his army was in no condition to fight for at least six weeks. This (armistice) would allow him time to recover.[27]

After the American victory at Monterrey, General Taylor’s strategy was to cut off the northern Mexican provinces, instead of occupying Mexico City. Taylor could conquer these territories and secure them for the United States. General Taylor believed the United States would incorporate these territories upon the official end of the war, which he believed his successful campaign had secured. Instead, General Taylor received orders from Washington to stay at Monterrey;[28] General Winfield Scott was planning and organizing a campaign to capture Mexico City.

The Mexicans used the eight-week armistice, after the battle at Monterrey, to reorganize their forces. This hiatus also allowed Antonio Lopez de Santa Anna, who had recently returned to power, to arrive and take control of the army. He ordered all the detachments of the army to his position in northern Mexico, for a last climatic showdown with Taylor in the north, and then he planned to take the war into Texas.

While General Taylor’s Army of Occupation was idle, General Scott began taking troops from him for his campaign for the Mexican capital. It was at this point, on February 22, 1847, that Santa Anna arrived to fight what he hoped would be the climatic battle of the war, the Battle of Buena Vista. The Americans, noting that the battle began on Washington’s Birthday, used this as a rallying cry for success of the battle. An army of volunteers valiantly fought and won this battle, since General Scott had detached most of the regulars to his army. Though outnumbered by a considerable amount, General Taylor put up such a convincing fight that Santa Anna withdrew and conceded the victory to the Americans.

In St. Louis, a force led by Colonel Alexander Doniphan, made up of the First Missouri Mounted Infantry, began an overland march to join the forces that occupied Santa Fe. When this force arrived in Santa Fe, they received orders to report to General Taylor’s army near Buena Vista. The area around Santa Fe could not support the amount of troops that occupied the town. Colonel Doniphan marched his men 3,500 miles across what became the southwest United States and northern Mexico - the worst land in the country.[29] These men marched over mountains and through deserts with limited supplies. They lived off the land as much as possible. When Colonel Doniphan returned to St. Louis, his troops were welcomed back as heroes.

General Scott began gathering his army on Lobos Island, Texas and on March 9, 1847, he landed his army near Vera Cruz, Mexico which is on the eastern coast of Mexico. Scott knew that the malaria season would begin soon so he immediately began siege operations. His men began digging trenches and emplacements for his cannons. Scott quickly learned that the cannons he brought with him were not of sufficient caliber to force the Mexicans out of the city. He borrowed some heavy cannon from the Navy. On March 29, 1847, Vera Cruz surrendered.

With the successful capture of Vera Cruz, General Scott began moving inland, away from the lowlands near the coast, to the highlands, away from the mosquitoes. He marched unopposed until he reached the vicinity of Cerro Gordo in Mexico. Santa Anna moved his army here, blocking the road to Mexico City. A young Captain Robert E. Lee, of General Scott’s staff, found a path through the wilderness that allowed the army to pass and flank the Mexican lines.[30] This allowed General Scott to attack Santa Anna’s army in the front and rear, simultaneously, which routed the Mexican army.

The American army moved into the highland town of Puebla, only two hundred miles from Mexico City, to rest and refit. Scott had to secure his supply line and await reinforcements as many of the volunteer regiments had served their year and returned home. This rest period allowed his men to return from the sick list, which included over a thousand men, but, with the arrival of warm weather, many would catch Yellow Fever.[31] Santa Anna also used this time to gather up his scattered army and begin preparing for the defense of Mexico City.

While in Puebla, Nicholas Trist arrived as President Polk’s emissary to the Mexican government. He carried with him a draft of a peace treaty that he was to present to the President of Mexico.[32] When Trist arrived at Puebla, he and Scott did not get along; Scott may have felt a threat to his political aspirations. Scott thought that the President was trying to “degrade” him by giving Trist authority to end the war.[33] To complicate matters, Trist was under orders not to reveal his plan to General Scott.[34] They continued to argue until the men received orders from Washington to stop. In time the men worked out their problems out and became best friends.

When General Scott began moving his army away from Puebla on August 7, 1847, he had an army of over 14,000 men but faced a Mexican army estimated at over 36,000 men. While the American army rested at Puebla, they drilled and honed their trade; they would be prepared for the resistance that the Mexican army displayed in the Valley of Mexico.

Scott’s first task was getting his army into position to reduce the Mexican forces located at Contreras and San Antonio. The geography of the land forced General Scott to devise a two-pronged assault, as a large area of impassible rocks divided the Mexican positions. American General Persifor Smith’s brigade attacked and crushed the Mexican detachment at Contreras in seventeen minutes.[35] Captain Robert E. Lee found a path through the rocks, which allowed the other force to flank the Mexican detachment at San Antonio. The fall of Contreras allowed the American force to help flank the Mexican’s at San Antonio. The American forces captured many Mexicans on the road to Churubusco.

In two and a half hours, the American troops reduced the Mexican position and captured Churubusco. General Scott could have moved into the city, but Santa Anna requested a truce. General Scott believed that Santa Anna would soon sue for peace, but he was mistaken. Santa Anna used the truce to gather his forces again and ready another defensive line closer to Mexico City. The soldiers in the American army knew this also. Future Major General George Gordon stated about the truce, “…had been most successful in giving Santa Anna time to repair his losses, replace his material, and increase the morale of his army.”[36]

On September 7, 1847, the truce failed, as the politicians could not secure a peace treaty. Upon the failure of the truce, General Scott moved into action. Scott began moving closer to Mexico City. His first assault against the city was launched at Molino del Rey. Santa Anna had sent five brigades to Molino del Rey as reinforcements, which was a surprise to the American forces since they were not expecting a major battle. Scott wrote in his autobiography that he had expected a smaller fight.[37] Though the battle was short, the casualties were extremely high for such a small American force, but, ultimately, the Mexicans endured another defeat to add to the growing list of defeats.

After General Scott’s victory at Molino del Rey, there was just one more position that had to be taken - Chapultepec. Chapultepec was once the Mexican Military Academy and stood on a key piece of ground outside the gates of Mexico City. Santa Anna placed over 600 men inside the fort to defend it. The only way for the Americans to reach the fort was with scaling ladders. General Scott ordered the assault to begin on September 13, 1847, even though he was unsure if the attack would succeed.[38] The ladders were late arriving, which caused considerable casualties among the American troops. Once inside the fort, the troops fought hand-to-hand until the Mexicans gave way. Santa Anna lost 1,800 men that day. Under cover of night, Santa Anna abandoned Mexico City to the Americans. A few American commanders flushed with victory, secured a gate to the city and entered. General Scott entered Mexico City on September 14, 1847. The military phase of the war was over, now the negotiators began their work.

Santa Anna was not yet ready to end the fight. He planned to move his army to Puebla, his hometown, which would cut General Scott’s supply line and force him to abandon Mexico City. Unfortunately for Santa Anna, he could not convince his generals to support him, as they realized the war was lost. Santa Anna would once again disappear from the Mexican scene, but not for long.

With the American army occupying Mexico City, it was time for the politicians to win the peace. Nicolas Trist, President Polk’s appointed negotiator, planned to continue his previously unsuccessful efforts. Trist was a strong willed politician who wanted to end the war with Mexico. Polk, frustrated with Trist, ordered him back to Washington. Trist refused to return to Washington when ordered to do so by President Polk. He stated his reason for his disobedience in a sixty plus page letter to Secretary Buchanan.[39] He felt he must stay to negotiate, because he feared that Mexico might sink into anarchy. He also felt the new ambassadors might not be able to salvage what Trist had already started.[40]

Mr. Trist’s negotiations paid off on February 2, 1848. The Mexicans signed the Treaty of Guadalupe Hidalgo. They gave up all the territory that would become the American Southwest and agreed on a Texas border along the Rio Grande River. The United States paid fifteen million dollars to the Mexican government.[41] The United States Senate ratified the treaty on March 10, 1848, officially ending the war.

The Americans fought the Mexican-American War to annex Texas into the United States, at the request of the Republic of Texas.[42] More than that, this war resulted in Mexico losing the territory that would form the American Southwest and the state of California, (gold would soon be discovered in California). The war also prevented Texas from falling to a powerful maritime or military foreign power, such as England.[43] As soon as this war ended another began, a political war. A war waged on the House and Senate floors between Whigs and Democrats of the United States Congress. The contemporary journals were politically driven and their outlook on the war was strikingly different. The American Whig Review called the war “a war of aggression and rapacity”[44] The Democratic Review stated “we have borne our wrongs from her (Mexico) with patience, until patience has ceased to be a virtue.”[45]

Southern Democrats wanted the new territory admitted to the Union as slave states, while Whigs and northern Democrats wanted the territory as “free soil”. Abolitionists feared Texas would be divided into numerous slave states, tipping the balance of power in Congress back to the southern states. The Democrats believed that “the theory of our domestic institutions, the provisions of our constitution, and the conflicting opinions of politicians on slavery, have nothing, or should have nothing to do with the broad question of our relations with Mexico. This is an independent topic, and should be treated as such.”[46] These words and many others were the opening shots of a new decade, the 1850’s, that saw the death of the Whig Party and the rise of a new political party, the Republican Party.

The Mexican-American War, as with all wars, caused more problems than the ones that started it. This nation’s desire to reach from coast to coast was so strong that the Americans overlooked the potential consequences. In the end, Manifest Destiny nearly destroyed the United States, sixteen years after the Mexican-American War.
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Show Footnotes and Bibliography

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Copyright © 2008 Phillip Muskett 

Written by Phillip Muskett. If you have questions or comments on this article, please contact Phillip Muskett at:

About the author:
Phillip Muskett was born in Gadsden Alabama, enlisted in the Navy in 1986 and retired after 20 years as a Chief Petty Officer. He Graduated from American Military University with a Masters Degree in Military Studies/American Civil War in 2007. He currently works in the DC/Baltimore area and has led a few tours for MHO. He currently resides in Westminster, Maryland.

Published online: 07/13/2008.

* Views expressed by contributors are their own and do not necessarily represent those of MHO.
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