Mexican War Summary

  • Last updated on November 10, 2022

The U.S. annexation of Texas violated what Mexico believed to be its national sovereignty over the territory and simultaneously created a significant border between the United States and Mexico. One year later, war broke out between the two countries, and Mexico was forced to cede half of its territory to the United States.

Summary of Event

The annexation of Texas Texas;annexation by United States by the United States in 1845 precipitated a major crisis in relations between Mexico and the United States. President Andrew Jackson Jackson, Andrew [p]Jackson, Andrew;and Texas[Texas] had recognized Texan independence in 1837, but fearing the addition of another slave state to the union, antislavery forces and northern Whigs Whig Party (American);and Texas annexation[Texas annexation] successfully blocked efforts to annex the Texas Republic. In 1843, Antonio López de Santa Anna warned that U.S. annexation of Texas, a province over which Mexico still claimed sovereignty, would be equivalent to declaring war against the Mexican Republic. In April, 1844, Sam Houston Houston, Sam , the president of the Texas Republic, accepted the U.S. offer for annexation, on the condition that United States military and naval protection would be forthcoming as a defense against any Mexican invasion. The U.S. Senate, however, rejected the proposed annexation treaty in June. Mexican War (1846-1848) Mexico;and United States[United States] Santa Anna, Antonio López de [p]Santa Anna, Antonio López de;and Mexican War[Mexican War] Polk, James K. [p]Polk, James K.;and Mexican War[Mexican War] Taylor, Zachary [p]Taylor, Zachary;and Mexican War[Mexican War] [kw]Mexican War (May 13, 1846-Feb. 2, 1848) [kw]War, Mexican (May 13, 1846-Feb. 2, 1848) Mexican War (1846-1848) Mexico;and United States[United States] Santa Anna, Antonio López de [p]Santa Anna, Antonio López de;and Mexican War[Mexican War] Polk, James K. [p]Polk, James K.;and Mexican War[Mexican War] Taylor, Zachary [p]Taylor, Zachary;and Mexican War[Mexican War] [g]United States;May 13, 1846-Feb. 2, 1848: Mexican War[2400] [g]Central America and the Caribbean;May 13, 1846-Feb. 2, 1848: Mexican War[2400] [g]Mexico;May 13, 1846-Feb. 2, 1848: Mexican War[2400] [c]Wars, uprisings, and civil unrest;May 13, 1846-Feb. 2, 1848: Mexican War[2400] [c]Expansion and land acquisition;May 13, 1846-Feb. 2, 1848: Mexican War[2400] Scott, Winfield [p]Scott, Winfield;and Mexican War[Mexican War] Slidell, John Trist, Nicholas Tyler, John [p]Tyler, John;and Texas annexation[Texas annexation] Herrera, José Joaquín Paredes y Arrillaga, Mariano

In May, the Democratic Party convention had nominated an ardent expansionist, James K. Polk Polk, James K. [p]Polk, James K.;and Texas annexation[Texas annexation] , for president, Presidency, U.S.;election of 1844 and in its campaign platform the party advocated the annexation of Texas and the acquisition of the whole of Oregon. The Whig Whig Party (American);and Texas annexation[Texas annexation] Party nominee, Henry Clay, who tried to avoid these expansionist issues, lost the election by a narrow margin. Viewing Polk’s victory as a public mandate for Texas annexation, President John Tyler recommended that the lame duck Congress by joint resolution offer to annex Texas. A joint resolution required only a simple majority vote of both Houses, whereas a treaty could be ratified only by a two-thirds vote of the Senate. Congress passed the resolution in February, and President Tyler signed it on March 1, 1845, three days before Polk’s inauguration. Mexico then broke off diplomatic relations with the United States.

Polk, Polk, James K. [p]Polk, James K.;and Texas annexation[Texas annexation] accepting Tyler’s Tyler, John [p]Tyler, John;and Texas annexation[Texas annexation] action, came to office with half of his party’s foreign policy platform virtually accomplished. Texas formally entered the union in December, but the explosive Texas question remained to be settled with Mexico. The immediate issue was a boundary dispute, with Polk supporting Texas’s questionable claim to the Rio Grande as its southwestern frontier rather than the Nueces River, farther north. In June, Polk ordered Brigadier General Zachary Taylor to move his forces into the disputed area, and by July, Taylor had established a base on the south bank of the Nueces River near Corpus Christi. In November, upon receiving confirmation that the Mexican government was prepared to receive a commissioner to discuss the boundary issue, Polk dispatched John Slidell Slidell, John , a Louisiana politician, to Mexico as minister plenipotentiary. Polk instructed Slidell to discuss three other outstanding issues: the purchase of California, the purchase of New Mexico, and the payment of damages to U.S. nationals for losses incurred in Mexican revolutions. Slidell was authorized to offer twenty-five million dollars for California and five million dollars for New Mexico and to propose United States assumption of U.S. damage claims against the Mexican government in return for its recognition of the Rio Grande boundary.

Slidell reached Mexico City on December 6. The government of acting president José Joaquín Herrera Herrera, José Joaquín , in response to growing domestic opposition to negotiations, refused to receive him. On January 13, 1846, the day after Slidell’s report of the refusal reached him, Polk ordered Taylor to advance through the disputed territory to the Rio Grande. In late December, the Herrera government had been overthrown, in part because of its alleged lack of firmness toward the United States. The new president, General Mariano Paredes y Arrillaga Paredes y Arrillaga, Mariano , reaffirmed Mexico’s claim to Texas and pledged himself to defend Mexican territory. On March 12, 1846, replying to Slidell’s final inquiry, Paredes, too, refused to receive the U.S. minister.

Slidell reported to Polk in Washington on May 8. The next day, news arrived from Taylor that on April 25, a large Mexican force had crossed the Rio Grande and surrounded a smaller U.S. reconnaissance party; when the U.S. party attempted to break out of the encirclement, eleven of its members were killed and the rest wounded or captured. The cabinet endorsed an immediate request for a declaration of war. In Polk’s war message, which he delivered to Congress on May 11, the president reviewed the boundary and claims issues and then concluded: “Mexico has . . . shed American blood upon American soil. . . . War exists . . . by the act of Mexico herself.” On May 13, he signed the declaration. Already, Taylor had fought and won the battles of Palo Alto and Resaca de la Palma, and on May 18, he occupied Matamoros.

Battle Sites in the Mexican War





Polk’s strategy was to occupy Mexico’s northern provinces, blockade Mexican ports, and conquer New Mexico and California. By September, Taylor’s army had taken Monterrey in northern Mexico, but not without heavy casualties, as the Mexicans battled fiercely to defend their city. By January, 1847, U.S. forces were also victorious in the West and had secured New Mexico and California. Although successful militarily, the strategy failed to bring Mexico to terms, because the United States demanded too much Mexican territory. In order to bring an end to the war, Polk decided to shift the major military effort from the northern periphery to the heart of Mexico. The plan called for Major General Winfield Scott Scott, Winfield [p]Scott, Winfield;and Mexican War[Mexican War] to take Veracruz, march through the mountains, and capture Mexico City;U.S. occupation of Mexico City.

U.S. forces entered Veracruz on March 29, 1847, following a weeklong land and naval bombardment, and on April 8, Scott’s army set out along the National Road for the Valley of Mexico. Paredes Paredes y Arrillaga, Mariano had been deposed in August, 1846, and the new Mexican provisional president was General Antonio López de Santa Anna. In September, he had taken an army north to oppose Taylor. The two armies met at Buena Vista in February, 1847, in a hotly contested battle. Both sides would later claim victory. Santa Anna then returned to central Mexico, where he prepared to repulse Scott’s invasion.

On April 18, Scott defeated Santa Anna at Cerro Gordo, and on May 15, he reached Puebla, only seventy-five miles from Mexico City. After a ten-week delay waiting for reinforcements and hoping to negotiate, Scott resumed the advance, again defeating Santa Anna’s forces in bloody encounters at Contreras and Churubusco. Santa Anna retreated to Mexico City, and an armistice was effected to allow the Mexican government to consider U.S. peace proposals delivered by Nicholas Trist Trist, Nicholas , who met with a Mexican commission headed by former president José Herrera. Herrera, José Joaquín

General Winfield Scott leading U.S. troops into Mexico City.

(C. A. Nichols & Company)

The Mexicans were prepared to surrender Upper California and give up claims to Texas. However, they refused to relinquish New Mexico New Mexico;and Mexico[Mexico] and demanded an independent buffer state between the Rio Grande and the Nueces River. Finally, the Mexicans demanded that no territory they surrendered should permit slavery, Slavery;and Mexico[Mexico] Mexico;and slavery[Slavery] which had been abolished in Mexico. The United States refused such conditions, and the two armies met at Molino del Rey and Chapultepec. The student cadets at the military college gallantly defended Chapultepec and have entered Mexican folklore as the Boy Heroes.

Scott Scott, Winfield [p]Scott, Winfield;and Mexican War[Mexican War] entered the capital on September 14, 1847. Santa Anna had fled the country, and the interim Mexican president, Pedro María Anaya (1795-1854), Anaya, Pedro María informed Trist Trist, Nicholas that he was prepared to negotiate. Negotiations were actually conducted with the next acting president, Manuel de la Peña y Peña (1789-1850). Peña y Peña, Manuel de la The resulting Treaty of Guadalupe Hidalgo, signed February 2, 1848, ended the war. The treaty was ratified by the U.S. Senate March 10, 1848.


Under the terms of the Treaty of Guadalupe Hidalgo Guadalupe Hidalgo, Treaty of (1848) , the U.S.-Mexico boundary was set at the Rio Grande, Gila, and Colorado Rivers, Colorado River and Mexico relinquished New Mexico and Upper California. In return, the United States paid Mexico $15 million and assumed the $3.25 million in claims of its citizens. Five years later, the United States negotiated the Gadsden Purchase (1853) Gadsden Purchase (1853) , adding what would become Arizona and southern New Mexico to its territory. By the end of 1853, the United States had acquired all of the Mexican territory that would eventually consitute the continental United States.

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">Bauer, K. Jack. The Mexican War, 1846-1848. Lincoln: University of Nebraska Press, 1992. New edition of a thorough account of the politics, diplomacy, and battles of the Mexican War. Several good maps of battlefields and photographs of participants on both sides.
  • citation-type="booksimple"

    xlink:type="simple">Bergeron, Paul H. The Presidency of James K. Polk. Lawrence: University Press of Kansas, 1987. A history of the Polk administration, which suggests that Polk was less than forthright in his refusal to make public his opinion on Mexico before taking office.
  • citation-type="booksimple"

    xlink:type="simple">Eisenhower, John S. D. Agent of Destiny: The Life and Times of General Winfield Scott. New York: Free Press, 1997. Eisenhower, a military historian (and son of former president Dwight D. Eisenhower) provides a detailed account of Scott’s military actions and the politics behind them. He portrays Scott as a courageous soldier and skilled military manager whose character was marred by ambition and vanity.
  • citation-type="booksimple"

    xlink:type="simple">______. So Far from God: The U.S. War with Mexico, 1846-1848. New York: Random House, 1989. Detailed account of the strategy of war and the battles, much of it taken from diaries and journals of the participants.
  • citation-type="booksimple"

    xlink:type="simple">Francaviglia, Richard V., and Douglas W. Richmond, eds. Dueling Eagles: Reinterpreting the U.S.-Mexican War, 1846-1848. Fort Worth: Texas Christian University Press, 2000. Series of essays, some written by Mexican scholars, reinterpreting the war from both a twentieth century and a Mexican perspective.
  • citation-type="booksimple"

    xlink:type="simple">Haecker, Charles M., and Jeffrey G. Mauck. On the Prairie of Palo Alto: Historical Archeology of the U.S.-Mexican War Battlefield. College Station: Texas A&M Press, 1997. Detailed analysis of the battle, producing scientific data that has altered long-established beliefs about the positions and movements of the armies at Palo Alto.
  • citation-type="booksimple"

    xlink:type="simple">Johannsen, Robert. To the Halls of Montezuma: The Mexican War in the American Imagination. New York: Oxford University Press, 1985. Discusses how contemporaries saw the Mexican War and is especially perceptive about why Zachary Taylor became a hero and Scott did not.
  • citation-type="booksimple"

    xlink:type="simple">Langley, Lester D. America and the Americas: The United States in the Western Hemisphere. Athens: University of Georgia Press, 1989. Places events of the Mexican War within the ongoing relationship between the United States and all Latin American nations. Raises issues of possible British influence in Texas and the importance of California to Polk.
  • citation-type="booksimple"

    xlink:type="simple">Mahin, Dean B. Olive Branch and Sword: The United States and Mexico, 1845-1848. Jefferson, N.C.: McFarland, 1997. A diplomatic history of the Mexican War, focusing on the policies of the Polk administration and the negotiations of American diplomat Nicholas Trist.
  • citation-type="booksimple"

    xlink:type="simple">Santoni, Pedro. Mexicans at Arms: Puro Federalists and the Politics of War, 1845-1848. Fort Worth: Texas Christian University Press, 1996. An analysis of Mexican political and military history during the period of the Mexican War.
  • citation-type="booksimple"

    xlink:type="simple">Scheina, Robert L. Santa Anna: A Curse upon Mexico. Washington, D.C.: Brassey’s, 2002. Military and political history of Santa Anna, depicting him as a political opportunist but a brave and resourceful military leader.
  • citation-type="booksimple"

    xlink:type="simple">Schroeder, John H. Mr. Polk’s War: American Opposition and Dissent, 1846-1848. Madison: University of Wisconsin Press, 1973. Provocative study of public opinion during the Mexican War. Conclusion is that Polk not only decided on the war before learning of the firing on American troops but also welcomed the conflict as a way to fulfill his expansionist plans.
  • citation-type="booksimple"

    xlink:type="simple">Winders, Richard Bruce. Mr. Polk’s Army: The American Military Experience in the Mexican War. College Station: Texas A&M Press, 1997. Using diaries, journals, and reminiscences, Winders recounts the daily life of soldiers who fought the war, analyzing the cultural, social, and political aspects of the army. He also contrasts the leadership styles of Generals Taylor and Winfield Scott.

Hidalgo Issues El Grito de Dolores

Mexican War of Independence

Texas Revolution

Battle of Palo Alto

United States Occupies California and the Southwest

Battle of Chapultepec

Treaty of Guadalupe Hidalgo Ends Mexican War

Gadsden Purchase Completes the U.S.-Mexican Border

Walker Invades Nicaragua

France Occupies Mexico

Díaz Drives Mexico into Civil War

Related Articles in <i>Great Lives from History: The Nineteenth Century, 1801-1900</i>

Sam Houston; Andrew Jackson; James K. Polk; Antonio López de Santa Anna; Winfield Scott; Zachary Taylor; John Tyler. Mexican War (1846-1848) Mexico;and United States[United States] Santa Anna, Antonio López de [p]Santa Anna, Antonio López de;and Mexican War[Mexican War] Polk, James K. [p]Polk, James K.;and Mexican War[Mexican War] Taylor, Zachary [p]Taylor, Zachary;and Mexican War[Mexican War]

Categories: History