Mexican War

n.

A war (1846–1848) between the United States and Mexico, resulting in the cession by Mexico of lands now constituting all or most of the states of California, Arizona, New Mexico, Nevada, Utah, and Colorado.

Mexican war (1846-8), the first successful international war of USA ‘manifest destiny’ imperialism, in which Pres Polk provoked a border dispute in order to seize the New Mexico territory (all of today's south-western states) and California. Mexico had not accepted the independence of Texas, still less its claim to the strip between the Nueces river and the Rio Grande. Following American annexation of Texas in early 1845, a US army of ‘observation’ under Taylor moved from Louisiana to the Nueces strip. In May 1846, 3, 700 Mexicans attacked Taylor's 2, 300. Repulsed at Palo Alto and defeated at Resaca de la Palma, they fell back behind the Rio Grande. The USA declared war on the 13th.

In a murky episode which could well have defined the course of the war, Polk's agents encouraged the return to Mexico of exiled dictator Santa Anna in August 1846. He agreed to a face-saving formula whereby the USA would occupy Saltillo, Tampico, and Vera Cruz, after which he would sell the territories Polk wanted for the $30 million earlier refused by the Mexican government. Once back in power he demonstrated his unique ability to finance and raise armies, but to the end of his life he hoped for a payment of $3 million, fuelling suspicion that his military operations were designed to enforce the agreement. If so, his need to act the role of national saviour believably was discounted or misinterpreted, an expensive error. The USA was to pay or forgive over $20 million in 1848 and a further $10 million in 1854, plus the $70 million direct costs of the war itself.

The New Mexico and California territories fell early to a small expedition under Kearny. To his rear a revolt of Pueblo Indians and unreconciled Mexicans was crushed by Price in January 1847, while Doniphan with 600-700 Missouri volunteers overawed the powerful Navajo. The latter then rode into Mexico over appalling terrain, defeating a more numerous and entrenched enemy outside Chihuahua, after which he rode east to join the main army with captured guns in tow.

On the Rio Grande front, the Mexican commander ignored Santa Anna's order to fall back on Saltillo and fortified Monterrey. Taylor successfully assaulted the town in September, but permitted the defenders to retreat on terms including an undertaking that US forces would not advance for eight weeks. Taylor was convinced that an invasion from the north to Mexico City was not viable and underlined his conviction by delay. His army suffered most of the 9, 000 desertions during the war and lost at least as many more who refused re-enlistment or were sent home because of indiscipline.

Probably aware of this and informed that part of Taylor's army was being withdrawn for a seaborne expedition to Vera Cruz, Santa Anna attacked in February 1847 with 15, 000 men. At Buena Vista, south of Saltillo, he drove back Taylor's 5, 000 by sheer weight of numbers and would certainly have prevailed the next day. Instead he chose to retreat. Thereafter the theatre subsided into guerrilla warfare.

The navy duly captured Tampico and army commander Scott led the expedition to Vera Cruz, landing where Santa Anna had recommended in March 1847. The port fell to bombardment twenty days later. At Cerro Gordo in mid-April, a strong position designed by Santa Anna to keep the Americans in the lowland yellow-fever belt was outflanked with minimal casualties. No further organized resistance was encountered until the Americans approached Mexico City, where on 20 August Santa Anna's forces were defeated at the battles of Contreras and Churubusco, the latter featuring fanatical resistance by Irish deserters and volunteers organized in the San Patricio regiment. Last-ditch resistance was overcome at Molino del Rey on 8 September and at the fort of Chapultepec five days later, whose defenders included a group of boy military cadets, the niũos heróicos of Mexican folklore.

The Mexican war: Geo-political background and principal places
(Click to enlarge)

In these later battles fewer than 11, 000 Americans overcame 30, 000 defenders, inflicting 7, 000 casualties and capturing a further 3, 000, for a loss of only 3, 100 killed, wounded and missing. Overall, US forces suffered 5, 800 battle casualties and 11, 500 deaths by disease, 22 per cent of all involved. The Duke of Wellington, no less, said the Vera Cruz campaign showed Scott to be the greatest soldier living. Polk thought otherwise and denigrated his achievement, keeping him in Mexico while Taylor rode the victory bandwagon to the presidency, an objective that was to elude his superior in every respect four years later.

Bibliography

• Bauer, K. Jack, The Mexican War 1846-1848 (New York, 1974)

— Hugh Bicheno

(1846–48)

After weeks of fruitless diplomacy, the United States and the republic of Mexico declared war on each other in the spring of 1846. By the 1840s, many Americans held the view that the United States should reach from the Atlantic all the way to the Pacific Ocean. In 1844, Democrat James K. Polk of Tennessee ran for the presidency and won on a platform of expansionism, embracing the popular concept of “manifest destiny”—that God approved U.S. expansion throughout the continent. Polk opened diplomacy designed to redeem his campaign pledges to purchase California and other Mexican lands as well as to obtain the Oregon country from Britain. Considered in grand strategic terms, Polk intended to make the United States the undisputed national power on the North American continent and to obtain West Coast ports. The British agreed to an equitable treaty dividing Oregon, but no self‐respecting patriotic Mexican leader would be satisfied with any amount of money for California.

U.S. annexation of Texas sparked the war. The Texas Revolution of 1836 had won independence for the republic of Texas, but Mexico never officially recognized the loss of the province. Polk's predecessor, John Tyler, arranged the annexation of Texas into the United States in 1845 by a joint resolution of both Houses of Congress before Polk was sworn in. According to Mexico, the United States had torn away one of its provinces. The Mexican government rejected Polk's final offer of $35 million for California and other lands and dispatched military forces to the Rio Grande. It also rejected Texas and U.S. claims that the border extended south to the Rio Grande instead of the Nueces River.

On 23 April 1846, President Mariano Paredes announced that a state of “defensive” war existed between Mexico and the United States, in response to the violation of the Texas border by U.S. soldiers under Gen. Zachary Taylor, who marched under Polk's orders from Louisiana through Texas up to the Nueces River. On 25 April, Mexican and U.S. forces fought a skirmish between the Nueces and the Rio Grande. Eleven U.S. dragons were killed, five wounded and forty‐seven captured. It took several days for word of the skirmish to reach President Polk, who had previously decided on war even before Paredes's announcement. On 11 May, he asked Congress to acknowledge the state of war that Mexico had already announced, but did so with a resounding and controversial call: “American blood has been shed on American soil.” On 13 May, Congress strongly endorsed Polk's request, 174–14 in the House of Representatives and 40–2 in the Senate. Critics, mostly northern Whigs, condemned the president's action, asserting that he sought war to acquire more slave territory and denying that the disputed border area belonged to the United States.

Northern Mexico included two commercial centers, Santa Fe, New Mexico, and San Francisco, California. Lightly populated and distant from Mexico City, both provinces were difficult to defend. Polk met with his cabinet and formulated a remarkably ambitious strategy. He ordered U.S. soldiers to invade New Mexico, capture Santa Fe, then proceed to conquer California, where a naval squadron would assist them in securing the province. Meanwhile, General Taylor with less than 3,000 regulars would drive Mexican forces south of the Rio Grande, which the United States claimed as the international boundary. Polk assumed that if U.S. forces occupied the Rio Grande as well as key spots in New Mexico and California, Mexico would have no choice but to concede the fait accompli, and the United States would have won the war.

For their part, however, the Mexicans stood ready to fight, both for the defense of their territory and the future of their fledgling nation, which only twenty‐four years earlier had won its independence from Spain. Mexico possessed a tiny naval coast guard and on paper had a national army of more than 30,000 soldiers, over three times the U.S. Army's size at 8,500 officers and men. Numbers masked contrasts between the two armies, however. The Mexican Army was indifferently trained and unevenly equipped. Some units had enthusiastic officers, good weapons, and adequate supplies; others were deficient in all respects. Many Mexican officers held honorific commissions but knew little about military matters. The army had been involved with intrigues in the national capital, where commanders went in and out of favor with the political winds. Thus, the Mexican Army had more weaknesses than strengths. In contrast, the United States possessed an excellent navy, which could dominate the Gulf of Mexico and the California coast. The U.S. Army had competent officers, excellent weapons, good training, and the advantage of a uniform supply system. Many of its company officers (captains and lieutenants) were graduates of the U.S. Military Academy at West Point, where they received training and education in weaponry and engineering. Many Mexican officers lacked these fundamentals and had no common base of education. U.S. artillery units were particularly noted for their high quality. Although it was smaller, the U.S. Army was superior to the Mexican Army.

But the regular U.S. Army would have to be supplemented by state volunteer units. President Polk asked Congress to approve a call for thousands of volunteers, prompting an initial positive response across the country. Dozens of state volunteer regiments were recruited for federal service, giving the United States the minimum manpower it needed to fight a war over a broad expanse of territory. Approximately 73,500 volunteers served in 1846–48.

While Congress considered the issue of war, soldiers fought the first major battle above the Rio Grande at a spot called Palo Alto (near Brownsville, Texas). Leading the U.S. forces, Zachary Taylor, a professional soldier since 1808, was an intuitive commander who had seen combat against Indian tribes. Taylor's force encountered the Mexican Army of the North, with about 6,000 soldiers, under Gen. Mariano Arista on 8 May 1846. The four‐hour combat was intense and indicated the bravery and dedication of the men on both sides, with each fielding some of the best regular units of their respective armies. Several times the Mexicans delivered strong charges into well‐directed U.S. artillery fire. The Americans repulsed the attacks and Arista elected to retreat. The next day, Taylor advanced his force to locate and fight the Mexicans, who had chosen defensive positions along an old path of the Rio Grande, the Resaca de la Palma. Taylor directed an assault that broke the Mexican line. Panic gripped some Mexican units and Arista and his officers could not prevent a rout. The U.S. victory inflicted serious casualties on some of the most well‐equipped Mexican Army units, which threw away arms and supplies in their hasty withdrawal. During the two days of combat, Taylor's army suffered less than 200 killed and wounded, but the Mexicans suffered more than 600 casualties. Arista retreated again, this time south of the Rio Grande.

In the weeks to come Taylor moved his army southward, occupying Matamoros, Mexico, on 17 May and Camargo on 14 July. Pressing deeper into Mexico, he fought a battle at Monterrey in late September, captured the city, then marched on to occupy Saltillo in November. The initial phase of the war had gone just as President Polk wanted. It had also made a national hero of General Taylor, who became a likely presidential nominee for the Whig Party.

Occurring simultaneously with part of Taylor's northern Mexico campaign was the U.S. invasion of New Mexico and California. The movement of multiple U.S. units threatened the Mexicans with a cordon offensive; that is, the U.S. forces put more than one offensive action into motion at almost the same time, not allowing the Mexicans to focus only on a single campaign.

Under orders from President Polk, Col. Stephen Watts Kearny mounted the campaign against Santa Fe from a training base at Fort Leavenworth (Kansas). Kearny led a mixed force of 1,600 soldiers (including 500 regulars), departing Leavenworth on 5 June and arriving at Santa Fe on 18 August after a grueling overland march. The Mexican authorities could neither raise nor send adequate military forces to resist Kearny, who entered the city unopposed. In only a few weeks, 1,000 more volunteers were expected to arrive, allowing Kearny to take the regulars in another overland march from Santa Fe to California, while 1,200 volunteers under Alexander Doniphan, a colonel of the Missouri volunteers, moved on El Paso del Norte (modern Juarez, Mexico).

The U.S. forces completed Polk's initial plan for the war without losing a battle. Kearny arrived in California in early December 1846. By that time U.S. sympathizers had declared the “Bear Flag Republic” on 4 July. U.S. naval forces under Commodore John D. Sloat had disembarked at Monterey 7 July, and another force under Commodore Robert Stockton had occupied Los Angeles 12 August. Meeting scattered resistance, the U.S. military forces appeared to have plucked California from Mexico like a bunch of grapes. Refusing to go down without a fight, Mexicans rose against the U.S. occupation in September and fought several skirmishes, the most important of which were at San Pasqual (northeast of San Diego) on 6 December 1846, and at San Gabriel on 8 January 1847. Following that U.S. victory, however, the province was effectively in North American hands.

In the meantime, on 25 December 1846, Doniphan's men defeated a Mexican force twice their size north of El Paso. Occupying El Paso, Doniphan waited for reinforcing artillery and then marched across inhospitably dry terrain toward Chihuahua. Outside the city, a hastily trained, inadequately equipped army opposed him. Deep in enemy territory with little prospect of support, Doniphan decided to attack the Mexican Army, although his men were again outnumbered more than two to one. The battle of 28 February 1847 sent the Mexicans into headlong retreat and allowed Doniphan to occupy Chihuahua.

North Americans had invaded Mexican territory in several places and been victorious in all of the war's opening campaigns. Yet the Mexican government refused to acknowledge defeat. Until a treaty confirmed Mexico's loss of California and New Mexico, the United States could not officially claim those vast territories.

Even before word of all the North American successes in California and the Southwest had reached Washington, President Polk and Winfield Scott, general in chief of the U.S. Army, had decided to open a new phase of the war. This would require another invasion of Mexico, intended to capture Mexico City itself. If Mexico's government would not concede defeat, then Polk intended to demand concessions at bayonet point in the enemy capital. Polk ordered Scott to assemble a strong expeditionary force by taking most of Taylor's regulars and supplementing them with several thousand volunteers and a few hundred U.S. Marines. The transfer of Taylor's regulars began 3 January 1847. Eased out of the war's climactic campaign, Taylor's temper flared at Polk as well as Scott. Brilliant, and something of a perfectionist, Scott plunged into plans for the expedition, including having special wooden landing boats built to carry his soldiers from ships offshore to the Mexican beaches. The Mexican port city of Veracruz on the Gulf of Mexico was selected as the U.S. base of operations, which meant that the port would have to be taken as the first step of the campaign. Scott prepared to launch his invasion in early March.

The Mexicans were not standing idle during the U.S. preparations. Their new and controversial president, Gen. Antonio Lopez de Santa Anna, envisioned a daring gamble that might yet turn the tide of the war. Demonstrating his inspirational leadership, Santa Anna created a new field army of 25,000 soldiers though the Mexican treasury was all but empty. Several of the units were brand‐new. A number had inadequate equipment and supplies, but there was a remarkable patriotic fervor as recruits and veterans marched north to carry out their president's risky design. A captured letter informed Santa Anna of Scott's campaign plan. Therefore, Santa Anna intended to defeat Taylor's reduced army (numbering less than 5,000), encamped near Buena Vista ranch, not far from Saltillo, then return to his capital and blunt the new American threat to the heart of Mexico. To reach Buena Vista, Santa Anna sent his men over 400 miles of rough terrain in the winter. This audacious plan missed succeeding by only a narrow margin.

On 22 February 1847, Santa Anna's army attacked Taylor's near Buena Vista in a series of piecemeal assaults turned back by blistering U.S. artillery fire. The next day, the Mexicans seemed on the verge of breaking through the U.S. line when they were met by a sharp counterattack led by Col. Jefferson Davis and his Mississippi volunteers. Relying on personal inspiration, Santa Anna persuaded his men to attack again, but again the North Americans repulsed them. The two armies glared at each other on the 23rd, and that night Santa Anna decided to retreat. The road south to Mexico City was littered with discarded weapons and wounded men. Santa Anna had lost almost 40 percent of his army killed, wounded, and missing. Taylor suffered around 700 killed and wounded some 15 percent of his army.

Upon his return to Mexico City, Santa Anna appealed to patriotism and used conscription. Drawing upon new taxes and extraordinary funds taken from the Catholic Church, he formed and began training another army. Meanwhile, Scott's expedition had landed below Veracruz on 9 March, laid siege to the city, and forced its garrison to surrender twenty days later. The North Americans organized the port as their base of operations and on 8 April Scott set out on the National Road to the capital.

Santa Anna hoped to bleed Scott's army (only about 14,000 at its strongest point) as it marched inland, forcing it to fight at roadblocks and weakening it to such an extent that it would either retreat or be vulnerable to a showdown battle. On 12 April at Cerro Gordo, about fifty miles from Veracruz, Santa Anna deployed 11,000 soldiers on a natural defensive position. Scott, however, had no intention of playing to Santa Anna's strengths. Using information brought by skilled staff officers—including Robert E. Lee, P. G. T. Beauregard, and George B. McClellan—Scott maneuvered his units in such a way as to outflank the Mexican defenses, dislodging Santa Anna and pushing him back on 18 April. U.S. Casualties were about 425 killed and wounded; Mexican losses were 1,000 killed and wounded and 3,000 taken prisoner.

Although he won the first encounter with Santa Anna, Scott had numerous problems. Diseases wracked his army. One thousand North Americans lay ill in hospitals in Veracruz, and another 1,000 were ill in Jalapa, a few miles west of Cerro Gordo. Moreover, the enlistment of thousands of volunteers expired in June. Scott held up his advance at Puebla on 15 May, sending the veterans home, awaiting the arrival of reinforcements, and buying provisions for his men. His army's enrollment stood at only around 7,000. The general determined that he could not garrison a string of depots or forts along the National Road and decided to cut himself off from his supply base (Veracruz) and live off the land, rendering his army even more vulnerable than before. However, using generous terms with local mayors and townsfolk, Scott maintained unusually good relations with the Mexican populace. Some guerrillas picked at the edges of his camps and line of march, but did not weaken him appreciably.

Commanding about 10,000 soldiers, Scott proceeded to the outskirts of Mexico City. Arriving near the capital in mid‐August 1847, the general again relied on his staff officers for reliable information about terrain and enemy strengths and weaknesses. Santa Anna had mustered nearly 25,000 men, mostly new recruits and national militia leavened with only a few thousand regulars, spread all around the city. Scott chose to approach from the south, crossing terrain that Santa Anna and his subordinates considered impassable, thus creating a measure of tactical surprise that gave him an advantage. The U.S. forces launched attacks against selected Mexican strongpoints, knowing that if they suffered serious losses they might yet be overwhelmed, just as Santa Anna envisioned. In a series of major battles between mid‐August and mid‐September, Scott's soldiers fought admirably, outflanking or breaking through well‐placed and often determined Mexican defenses, such as that conducted at the Battle of Chapultepec by regulars and cadets of the Mexican military academy. Scott's army suffered more than 3,000 killed, wounded, and lost to disease during the battles for the capital. On 14 September, the victorious U.S. forces entered the plaza of downtown Mexico City, ending a remarkable military campaign. Great Britain's duke of Wellington, who had declared the expedition lost when it cut loose from its supply line, now landed Scott's achievement.

Reinforced during the weeks to come, Scott's army occupied the capital for several months, employing an effective military government while diplomatic negotiations brought the war to an official end. Other army officers also provided governmental leadership for the territory of California from 1848 to 1850. No Mexican politicians wanted to affix their names to the treaty that would give up half of their country's territory to the United States. Finally, on 2 February 1848, the diplomats agreed to the terms of the Treaty of Guadalupe‐Hidalgo. The U.S. Senate ratified the treaty on 17 March. Both sides confirmed the agreement 30 May. The United States gained all of the vast lands Polk had sought at the beginning of the war—later to become the states of California, New Mexico, Arizona, Nevada, Colorado, and Utah—taking about half of the land of Mexico but only about 1 percent of its population. The Rio Grande would form part of the boundary between Texas and Mexico. In return, the United States agreed to pay Mexico $15 million and assume all claims of American citizens against the Mexican government, about another $3 million.

In addition to the territories lost by Mexico and gained by the United States, the war produced several other important results. After expending $100 million and losing more than 10,000 military personnel (killed or died of disease), the United States became a truly continental power, stretching from the Atlantic to the Pacific, and had a vast potential for the future. Only a few months after the war, gold was discovered in California, prompting a frantic rush of settlers from all parts of the world and making California eligible for statehood in 1850, ahead of expectations. Most of the West Point graduates had acquitted themselves with distinction during the war, confirming the place of the academy in American life. The U.S. Army had fought its first overseas war and its services of supply and recruitment had worked satisfactorily enough to give the nation a victory. Scott's campaign to capture Mexico City provided notable operations for U.S. military officers to study in the future. Although only a few U.S. Marines participated in that campaign their role received favorable publicity, helping to gain continued congressional support for the Marine Corps.

Moreover, the war produced notable political consequences. By his audacious decisions and detailed direction of the war, James K. Polk broadened the powers of the president as commander in chief. The Whigs nominated Zachary Taylor and he won the presidential election of 1848. In 1852, the Whigs nominated Winfield Scott, but he lost to his former subordinate, volunteer general and New Hampshire politician Franklin Pierce, the Democratic nominee. Debates intensified over the status of slavery in the new territories, leading most immediately to the Compromise of 1850. That measure admitted California as a free state but allowed slaveowners to bring slaves into the western territories captured from Mexico. Other provisions ended the slave trade in Washington, D.C., and provided a new Fugitive Slave Law. Thus, the successful war that expanded the United States to the Pacific also further intensified the debate over issues relating to slavery and led toward the sectional crisis of 1860, secession, and the U.S. Civil War.

[See also Academics, Service: U.S. Military Academy; Army, U.S.: 1783–1865; Civil War: Causes; Marine Corps, U.S.: 1775–1865; Mexican Revolution, U.S. Military Involvement in the; Texas War of Independence.]

Bibliography

• Ramon Alcaraz, The Other Side, trans. Albert C. Ramsey, 1850.
• Justin H. Smith, The War with Mexico, 2 vols., 1919.
• Robert S. Henry, The Mexican War, 1950.
• Otis A. Singletary, The Mexican War, 1960.
• George W. Smith and Charles Judah, eds., Chronicles of the Gringos: The U.S. Army in the Mexican War, 1968.
• David M. Pletcher, The Diplomacy of Annexation: Texas, Oregon, and the Mexican War, 1973.
• K. Jack Bauer, The Mexican War, 1974.
• John E. Weems, To Conquer a Peace, 1974.
• Robert W. Johannsen, To the Halls of the Montezumas, 1985

(1846-48) a war that vastly increased U.S. territory and contributed to the sectional crisis. Elected in 1844 on a platform of expansionism, James K. Polk moved quickly to fulfill his promises, obtaining Oregon from Britain and negotiating to buy California and other Mexican territories. Mexican President Mariano Paredes predictably rejected American offers. Already seething from the U.S. annexation of Texas in 1845 and the attempts to stretch the border to the Rio Grande, he declared a state of “defensive” war on April 23, 1846. When word of a Texas skirmish eventually reached Washington, Polk asked Congress to acknowledge war, which it did on May 13.

Although Mexico's regular army owned superior numbers, the U.S. army possessed better training, leadership, and weaponry; and over 73, 000 volunteers. The United States mounted several nearly simultaneous offensive actions. The fighting began on May 8, and Gen. Zachary Taylor's troops won the Battle of Palo Alto (near Brownsville, Texas). As they moved steadily southward, capturing Monterrey by late September and Saltillo in November, Col. Stephen Watts's troops easily occupied Santa Fe, from which they began an overland march to California. Aided by the navy, the army captured California by early January. Around the same time, Alexander Doniphan's forces occupied Chihuahua, and the United States won every battle in the first phase of the war.

While Polk and Winfield Scott drew up plans to capture Mexico City and thus force surrender, the new Mexican president, Gen. Antonio López de Santa Anna, rebuilt his army and prepared to attack Taylor's forces at Saltillo. Helped by an intercepted letter containing Santa Anna's plans and by Col. Jefferson Davis's Mississippi volunteers, Taylor withstood the attack. As Santa Anna retreated to the capital, Scott captured Veracruz, from where the march to Mexico City began. Scott's troops eventually reached the outskirts of the city by mid August, and, after a series of battles, U.S. forces entered Mexico City on September 14. The Treaty of Guadalupe-Hidalgo was signed on February 2, and confirmed by both sides on May 30, 1848, officially ended the war.

The United States gained the territories that would become California, New Mexico, Arizona, Nevada, Colorado, and Utah, and stretched the Texas border to the Rio Grande. On a federal level, Polk had greatly expanded the powers of the commander in chief. On the strength of his war record, Taylor won the 1848 election. Scott, in turn, was the Whigs' presidential nominee in 1852, but lost to his former subordinate, Democrat Franklin Pierce. Most importantly, the war heightened tensions over slavery, as a series of postwar measures granted slavery in California, abolished it in Washington, D.C., and created the new Fugitive Slave Law, thus bringing the country closer to the Civil War.

See the Introduction, Abbreviations and Pronunciation for further details.

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Mexican-American War (1846–1848). The war's remote causes included diplomatic indiscretions during the first decade of American-Mexican relations, as well as the effects of the Mexican revolutions, during which American citizens suffered physical injury and property losses. Its more immediate cause was the annexation of Texas. The Mexican government refused to recognize Texas as independent or the Rio Grande as an international boundary. It first withdrew its minister from Washington, D.C., and then severed diplomatic relations in March 1845.

President James K. Polk anticipated military action and sent Brigadier General Zachary Taylor with his force from Louisiana to the Nueces River in Texas, but he also sought a diplomatic solution. Recognizing that the chief aim of American foreign policy was the annexation of California, Polk planned to connect with that policy the adjustment of all difficulties with Mexico, including the dispute over jurisdiction in the territory between the Nueces River and the Rio Grande.

In September 1845, assured through a confidential agent that the new Mexican government of José Joaquín Herrera would welcome an American minister, and acting on the suggestion of Secretary of State James Buchanan, Polk appointed John Slidell as envoy-minister on a secret mission to secure California and New Mexico for $15 million to $20 million if possible, or for $40 million if necessary—terms later changed by secret instructions to $5 million for New Mexico and $25 million for California.

Mexico refused to reopen diplomatic relations. In January 1846, after the first news that the Mexican government, under various pretexts, had refused to receive Slidell, partly on the ground that questions of boundary and claims should be separated, Polk ordered Taylor to advance from Corpus Christi, Texas, to the Rio Grande, resulting shortly in conflicts with Mexican troops at the battle of Palo Alto on 8 May and the battle of Resaca de la Palma on 9 May. On 11 May, after arrival of news of the Mexican advance across the Rio Grande and the skirmish with Taylor's troops, Polk submitted to Congress a war message stating that war existed and that it was begun by Mexico on American soil. The United States declared war on 13 May, apparently on the ground that such action was justified by the delinquencies, obstinacy, and hostilities of the Mexican government; and Polk proceeded to formulate plans for military and naval operations to advance his goal of obtaining Mexican acceptance of his overtures for peace negotiations.

The military plans included an expedition under Colonel Stephen W. Kearny to New Mexico and from there to California, supplemented by an expedition to Chihuahua; an advance across the Rio Grande into Mexico by troops under Taylor to occupy the neighboring provinces; and a possible later campaign of invasion of the Mexican interior from Veracruz.

In these plans Polk was largely influenced by assurances received in February from Colonel A. J. Atocha, a friend of Antonio López de Santa Anna, then in exile from Mexico, to the effect that the latter, if aided in plans to return from Havana, Cuba, to Mexico, would recover his Mexican leadership and cooperate in a peaceful arrangement to cede Mexican territory to the United States. In June, Polk entered into negotiations with Santa Anna through a brother of Slidell, receiving verification of Atocha's assurances. Polk had already sent a confidential order to Commodore David Conner, who on 16 August permitted Santa Anna to pass through the coast blockade to Veracruz. Having arrived in Mexico, Santa Anna promptly began his program, which resulted in his own quick restoration to power. He gave no evidences whatever of his professed pacific intentions.

On 3 July 1846 the small expedition under Kearny received orders to go via the Santa Fe Trail from Fort Leavenworth, Kansas, to occupy New Mexico. It reached Santa Fe on 18 August, and a part of the force (300 men) led by Kearny marched to the Pacific at San Diego. From there it arrived at Los Angeles to join the forces led by Commodore Robert Field Stockton, including John Charles Frémont's Bear Flag insurgents. Kearny and Stockton joined forces and defeated the Mexican army at Los Angeles on 8 and 9 January 1847. On 13 January, Frémont and Andres Pico, the leader of the Mexican forces in California, signed the Treaty of Cahuenga. Kearny went on to establish a civil government in California on 1 March.

Taylor's forces, meanwhile, began to cross the Rio Grande to Matamoros on 18 May 1846 and advanced to the strongly fortified city of Monterrey, which after an attack was evacuated by Mexican forces on 28 September. Later, in February 1847 at Buena Vista, Taylor stubbornly resisted and defeated the attack of Santa Anna's Mexican relief expedition.

Soon thereafter the theater of war shifted to Veracruz, from which the direct route to the Mexican capital seemed to present less difficulty than the northern route. In deciding on the campaign from Veracruz to Mexico City, Polk probably was influenced by the news of U.S. occupation of California, which reached him on 1 September 1846. The U.S. Navy had helped secure Monterrey, San Diego, and San Francisco in California and had continued blockades against Veracruz and Tampico. The Navy provided valuable assistance again when General Winfield Scott began a siege of Veracruz. After the capture of the fortress of Veracruz on 29 March 1847, Scott led the army westward via Jalapa to Pueblo, which he entered on 15 May and from which he began his advance to the mountain pass of Cerro Gordo on 7 August.

Coincident with Scott's operations against Veracruz, Polk began new peace negotiations with Mexico through a "profoundly secret mission." On 15 April, Buchanan had sent Nicholas P. Trist as a confidential peace agent to accompany Scott's army. In August, after the battles of Contreras and Churubusco, Trist arranged an armistice through Scott as a preliminary step for a diplomatic conference to discuss peace terms—a conference that began on 27 August and closed on 7 September by Mexican rejection of the terms offered. Scott promptly resumed his advance. After hard fighting from 7 to 11 September at the battles of Molino del Rey and Chapultepec, he captured Mexico City on 14 September and with his staff entered the palace, over which he hoisted the American flag.

Practically, the war was ended. Santa Anna, after resigning his presidential office, made an unsuccessful attempt to strike at the American garrison Scott had left at Pueblo, but he was driven off and obliged to flee from Mexico.

The chief remaining American problem was to find a government with enough power to negotiate a peace treaty to prevent the danger of American annexation of all Mexico. Fortunately, Trist was still with the army and in close touch with the situation at the captured capital. Although recalled, he determined to assume the responsibility of remaining to renew efforts to conclude a peace treaty even at the risk of disavowal by his government. After some delay, he was able to conclude with the Mexican commissioners a treaty in accord with the instructions that had been annulled by his recall. The chief negotiations were conducted at Mexico City, but the treaty was completed and signed on 2 February 1848 at the neighboring town of Guadalupe Hidalgo. By its terms, which provided for cessation of hostilities, the United States agreed to pay $15 million for New Mexico and California. Polk received the treaty on 19 February and promptly decided to submit it to the Senate, which approved it on 10 March by a vote of thirty-eight to fourteen. Ratifications were exchanged on 30 May 1848.

Among the chief results of the war were expansion of American territory; a new population called Mexican Americans; increased American interest in the problems of the Caribbean and the Pacific and in the opening and control of isthmian interoceanic transit routes at Panama, Nicaragua, and Tehuantepec; and outbursts of "manifest destiny" from 1848 to 1860. The acquisition of Mexico's northern lands also intensified debates over the extension of slavery into new territory and brought the Union a step closer to war.

Bibliography

Connor, Seymour V., and Odie B. Faulk. North America Divided: The Mexican War, 1846–1848. New York: Oxford University Press, 1971.

Johannsen, Robert W. To the Halls of the Montezumas: The Mexican War in the American Imagination. New York: Oxford University Press, 1985.

McCaffrey, James M. Army of Manifest Destiny: The American Soldier in the Mexican War, 1846–1848. New York: New York University Press, 1992.

Robinson, Cecil, ed. and trans. The View from Chapultepec: Mexican Writers on the Mexican-American War. Tucson: University of Arizona Press, 1989.

Smith, George W., and Charles Judah, eds. Chronicles of the Gringos: The United States Army in the Mexican War, 1846–1848. Albuquerque: University of New Mexico Press, 1968.

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A war fought between the United States and Mexico from 1846 to 1848. The United States won the war, encouraged by the feelings of many Americans that the country was accomplishing its manifest destiny of expansion. Mexico renounced all claims to Texas north of the Rio Grande and yielded a vast territory that embraces the present states of California, Nevada, and Utah, and parts of Arizona, Colorado, New Mexico, and Wyoming.

Many generals of the Civil War, including Ulysses S. Grant and Robert E. Lee, gained experience in battle during the Mexican War. The Mexican War was opposed by many Americans, notably by the author Henry David Thoreau, who was put in jail for refusing to pay a tax to support the war. His essay “Civil Disobedience” explains the principles of his action.