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The Mexican American War: Timeline and Facts

What Caused the Mexican American War?
Theory 1: Simply stated, a dictatorial Centralist government in Mexico began the war because of the U.S. annexation in 1945 of Texas, which Mexico continued to claim despite the establishment of the independent republic of Texas 10 years before.

Theory 2: Some historians have argued, however, that the United States provoked the war by annexing Texas and, more deliberately, by stationing an army at the mouth of the Rio Grande.

Theory 3: Another, related, interpretation maintains that the administration of U.S. President James K. Polk forced Mexico to war in order to seize California and the Southwest.

Theory 4: A minority believes the war arose simply out of Mexico’s failure to pay claims for losses sustained by U.S. citizens during the Mexican War of Independence.

Timeline and Facts of the Mexican American War

Early 1845: President Antonio Lopez de Santa Ana is overthrown, followed by a power-struggle in which Jose Joaquin Herrera emerges as the new leader of Mexico.
March 1, 1845: U.S. President John Tyler signs Joint Resolution of Congress, offering Texas terms of annexation.
March 4, 1845: James Knox Polk inaugurated President of the United States.
March 31, 1845: Mexican Minister to the U.S., Juan Almonte, requests his passport and issues a proclamation that defames the U.S.A. and indicates a state of war exists.
April 5, 1845: Mexican President Herrera sends Antonio Lopez de Santa Ana into exile in Cuba.
June 4, 1845: Mexican President Herrera issues war proclamation.
July 1, 1845: US/Canadian Border Debate. The United States renews its compromise proposal of 49º north latitude for the U.S.-Canadian border line in Oregon Territory. Northwestern Democrats are embittered by this “betrayal” of Polk’s campaign promise of “54-40 or fight.”
July 4, 1845: Texas votes in favor of annexation.
July 1845: President James K. Polk orders General Zachary Taylor to organize an army for occupation of Corpus Christi, Texas and Commodore David Conner to prepare a squadron for the Gulf of Mexico.
October 1845: President Herrera agrees to meet US Commissioner John Slidell to discuss peace. Slidell is actually sent to discuss a bigger purchase.
OctoberNovember 1845: Rumors in Mexican press undermine Herrera by accusations he is a traitor intent on giving away Mexican land, so Herrera refuses to meet Slidell. Political opponents of Herrera call for military action.
December 1845: With troops intended for the border, General Mariano Paredes forces Mexican President Jose Joaquin Herrera from office.
January 1846: Mariano Paredes is new President of Mexico.
January 1846: President Polk orders Zachary Taylor and troops from Corpus Christi to Rio Grande and David Conner’s squadron to Vera Cruz.
March 18, 1846: In Matamoros, Mexican General Francisco Mejia issues a proclamation of war then sends it to Zachary Taylor.
April 25, 1846: Thornton Affair- US Dragoons attacked by Mexican Cavalry on US side of Rio Grande.
May 3-8, 1846: Fort Texas Siege
May 8, 1846: Battle of Palo Alto. The first major conflict of the Mexican-American War, the Battle of Palo Alto (fought just north of modern-day Brownsville, Texas) ends indecisively. U.S. General Zachary Taylor loses 9 men and 43 more are wounded; over 200 Mexican soldiers are killed and over 125 wounded.
May 9, 1846: Battle of Resaca de la Palma
May 9, 1846: News arrives in Washington of the Thornton Affair.
May 11, 1846: President Polk, who has been planning on declaring war against Mexico for almost a week, sends a war message to Congress on the first working day after hearing of the sixteen American casualties near the Rio Grande in Texas.
May 13, 1846: US Declares war on Mexico. President Polk says “American blood has been shed on American soil”.
April 25, 1846: Thornton Affair, South Texas
May 3-9 1846: Siege of Fort Texas, South Texas
May 8, 1846: Battle of Palo Alto, South Texas
May 9, 1846: Battle of Resaca de la Palma, South Texas. In the Battle of Resaca de la Palma, American forces under Gen. Zachary Taylor rout Mexican troops led Gen. Mariano Arista, who are forced to withdraw across the Rio Grande.
May 13, 1846: U.S. declares war against Mexico.
May 18, 1846: U.S. troops occupy Matamoros.
July,7 1846: U.S. Naval forces occupy Monterey, California.
July 14, 1846: U.S. forces occupy Camargo.
July 21, 1846: General Taylor issues orders for the discharge of 3 and 6 month volunteers.
July 30, 1846: General Taylor issues orders for movement of troops to Camargo.
August 8, 1846: In Congress, Democratic representative David Wilmot introduces the momentous antislavery amendment that later comes to bear his name: the Wilmot Proviso. What is the Wilmot Praviso? A proposed attachment to President Polk’s request for $2 million to fund the war and to buy territory, the proviso would grant the president his funds only if any territory acquired was made free soil. In the end, the Proviso passes the House but goes on to defeat in the Senate.
August 16, 1846: Santa Anna returns to Mexico from exile in Cuba.
August 18, 1846: U.S. forces under General Stephen W. Kearny occupy Santa Fé, New Mexico.
August 19, 1846: First U.S. troops depart Camargo for Monterey, Mexico.
September 19, 1846: Battle of Monterrey. The Battle of Monterrey commences when Gen. Zachary Taylor stations his 6,640 American soldiers north of the city and takes control of the roads. Mexican General Pedro Ampudia and his force of 5,000 are cut off from reinforcements, and Taylor mounts a two-pronged assault. After five days of fighting, Taylor grants Ampudia’s request for a parlay and the Mexican forces are permitted to leave with their weapons on 25 September.
October 7, 1846: Battle of Dominguez Rancho, Southern California.
November 14, 1846: U.S. Navy seizes Tampico.
November 16, 1846: U.S. forces occupy Saltillo. Battle of Natividad, Northern California.
December 6, 1846: Battle of San Pasqual, California.
December 25, 1846: Battle of El Brazito, New Mexico.
January 2, 1847: Battle of Santa Clara, California.
January 8, 1847: Battle of Rio San Gabriel, California.
January 9, 1847: Battle of La Mesa, California.
January 24, 1847: Battles of Cañada and Mora, New Mexico.
January 29, 1847: Battle of Embudo Pass, New Mexico.
February 3-4, 1847: Battle of Pueblo de Taos, New Mexico.
February 22-23, 1847: Battle of Buena Vista. President Polk, enraged with General Zachary Taylor for allowing Mexican forces to walk away armed after the Battle of Monterrey, transfers Taylor’s forces to join Gen. Winfield Scott’s invasion of central Mexico at Veracruz. To capitalize on the upheaval created by the transition in American troop assignments, Mexican General Santa Anna heads north from San Luis Potosí with an army of 20,000. At the battle of Buena Vista, Santa Anna’s forces break the American line by mid-day before Taylor’s reserves under the command of Colonel Jefferson Davis succeed in stalling the Mexican advance. Over 3,400 Mexican soldiers and about 650 Americans are killed.
February 28, 1847: Battle of the Sacramento, Northern Mexico
March 9, 1847: 10,000 U.S. troops landed on beaches by Navy at Vera Cruz.
March 9-29, 1847: Siege and bombardment of Vera Cruz.
March 29, 1847: Mexican forces at Vera Cruz capitulate.
April 18, 1847: Battle of Cerro Gordo.
June 6, 1847: Affair at Las Vegas, New Mexico.
August 19-20, 1847: Battles of Contreras and Churubusco.
September 8, 1847: Battle of Molino Del Rey.
September 13, 1847: Battle of Chapultepec.
September 13-14, 1847: Battle for Mexico City.
September 14 – October 12 1847: Siege of Puebla.
September 15, 1847: U.S. forces under General Winfield Scott occupy Mexico City.
October 9, 1847: Affair at Huamantla.
October 19, 1847: Affair at Atlixco.
December 1, 1847: Preparing for his annual message to Congress, President Polk plans to deliver a threat that more land cessions—in addition to California and the Southwest—will be necessary if Mexico protracts the war any further.
February 2, 1848: Treaty of Guadalupe Hidalgo signed, formally ending the war. California, Nevada, Utah, most of New Mexico and Arizona, and the disputed regions of Texas are all obtained by the United States in the largest single land acquisition since the Louisiana Purchase of 1803.
February 21, 1848: John Quincy Adams, staunch opponent of slavery and the only President to serve in Congress after his presidency, is struck with a fatal cerebral hemorrhage in his seat on the floor of the House and dies two days later.
March 10, 1848: U.S. Senate ratifies Treaty of Guadalupe Hidalgo, with amendments.
May 25, 1848: Mexican Congress ratifies Treaty of Guadalupe Hidalgo.
July 4, 1848: President Polk formally announces ratification of Treaty of Guadalupe Hidalgo.
August 2, 1848: Last U.S troops leave Mexico.