The Mexican War
The Mexican War between the United States and Mexico began with a Mexican attack on American troops along the southern border of Texas on Apr. 25, 1846. Fighting ended when U.S. Gen. Winfield Scott occupied Mexico City on Sept. 14, 1847; a few months later a peace treaty was signed (Feb. 2, 1848) at Guadalupe Hidalgo. In addition to recognizing the U.S. annexation of Texas defeated Mexico ceded California and , New Mexico (including all the present-day states of the Southwest) to the United States.
BACKGROUND
As with all major events, historical interpretations concerning the causes of the Mexican War vary. Simply stated, a dictatorial Centralist government in Mexico began the war because of the U.S. annexation (1845) of Texas, which Mexico continued to claim despite the establishment of the independent republic of Texas 10 years before. 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. 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. 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.
Mexican Politics
At the time of the war, Mexico had a highly unstable government. The federal constitution of 1824 had been abrogated in 1835 and replaced by a centralized dictatorship. Two diametrically opposed factions had arisen: the Federalists, who supported a constitutional democracy; and the Centralists, who supported an autocratic government under a monarch or dictator. Various clashing parties of Centralists were in control of the government from 1835 to December 1844. During that time numerous rebellions and insurgencies occurred within Mexican territory, including the temporary disaffection of California and the Texas Revolution, which resulted in the independence (1836) of Texas.
In December 1844 a coalition of moderates and Federalists forced the dictator Antonio Lopez de Santa Anna into exile and installed Jose Joaquin Herrera as acting president of Mexico. The victory was a short-lived, uneasy one. Although Santa Anna himself was in Cuba, other Centralists began planning the overthrow of Herrera, and the U.S. annexation of Texas in 1845 provided them with a jingoistic cause.
U.S. Policy
The U.S. annexation of Texas, by a joint congressional resolution (Feb. 27-28, 1845), had caused considerable political debate in the United States. The desire of the Texas Republic to join the United States had been blocked for several years by antislavery forces, who feared that several new slave states would be created from the Texas territory. The principal factor that led the administration of John Tyler to take action was British interest in independent Texas. Indeed, anti-British feeling lay behind most of the expansionist policy statements of the United States in this period. James Polk won the 1844 presidential election by advocating a belligerent stand against Britain on the Oregon Question. Once in office he declared that "the people of this continent alone have the right to decide their own destiny." About the same time the term Manifest Destiny came into vogue to describe what was regarded as a God-given right to expand U.S. territory. The term was applied particularly to the Oregon dispute, but it had relevance also to California, where American settlers warned of British intrigues to take control, and to Texas.
The Mexican Response and the Slidell Mission
As early as August 1843, Santa Anna's government had informed the United States that it would "consider equivalent to a declaration of war . . . the passage of an act for the incorporation of Texas." The government of Herrera did not take this militant position. It had already initiated steps, encouraged by the British, to recognize the independence of the Republic of Texas, and although Santa Anna's lame-duck minister in Washington broke diplomatic relations with the U.S. government immediately after annexation, in August 1845 the Herrera government indicated willingness to resume relations. Not only was the Herrera government prepared to accept the loss of Texas, but it also hoped to lay to rest the claims question that had plagued U.S.-Mexican affairs since 1825. Britain and France had used force, or the threat of it, to induce the Mexican government to pay their claims on behalf of their citizens. The United States, however, preferred to negotiate, and the negotiations had dragged on interminably.
Fearing that American patience was running short, Herrera seemed determined to settle the issue. He requested that the United States send a minister plenipotentiary to Mexico, and President Polk appointed John Slidell.
Slidell's authority, however, may have exceeded Herrera's intentions. Slidell was authorized to purchase California and New Mexico from Mexico and to settle the Texas boundary, which was a source of dispute even with the Mexican moderates. While the Republic of Texas had claimed the Rio Grande as its boundary, the adjacent Mexican state of Tamaulipas claimed the area north of the Rio Grande to the Nueces River.
By the time Slidell arrived in Mexico in December 1845, the Herrera government was under intense fire from the Centralists for its moderate foreign policies. The Centralist strategy was to appeal to Mexican national pride as a means of ousting Herrera. During August 1845 their leader, Mariano Parades y Arrillaga, began to demand an attack on the United States. When Slidell arrived, Herrera, in an effort to save his government, refused to meet with him. A few days later (December 14), Parades issued a revolutionary manifesto; he entered Mexico City at the head of an army on Jan. 2, 1846. Herrera fled, and Parades, who assumed the presidency on January 4, ordered Slidell out of Mexico.
After the failure of the Slidell mission, Polk ordered Zachary Taylor to move his army to the mouth of the Rio Grande and to prepare to defend Texas from invasion. Taylor did so, arriving at the Rio Grande on Mar. 28, 1846. Abolitionists in the United States, who had opposed the annexation of Texas as a slave state, claimed that the move to the Rio Grande was a hostile and aggressive act by Polk to provoke a war with Mexico to add new slave territory to the United States.
Whatever Polk's precise intentions were, for the Centralists in Mexico the annexation of Texas had been sufficient cause for war; they saw no disputed boundary--Mexico owned all of Texas. Before Taylor had moved to the Rio Grande, Parades had begun mobilizing troops and had reiterated his intention of attacking. On April 4 the new dictator of Mexico ordered the attack on Taylor. When his commander at Matamoros delayed, Parades replaced him, issued a declaration of war (April 23), and reordered the attack.
NORTHERN MEXICAN CAMPAIGN
On Apr. 25, 1846, Mexican troops crossed the Rio Grande and ambushed a detachment of American dragoons commanded by Capt. Seth B. Thornton. Taylor's report of this ambush reached President Polk on the evening of May 9, a Saturday. On Monday, May 11, Polk presented his war message to Congress, and on Wednesday, May 13, over the vigorous opposition of the abolitionists, the U.S. Congress voted to declare war on Mexico. In the meantime two more Mexican attacks had been made across the Rio Grande at Palo Alto (May 8) and Resaca de la Palma (May 9), and both had been repulsed.
Mexican Expectations
Mexican leaders clearly expected to win these battles as well as to recover Texas and win the war. Parades spoke grandly of occupying New Orleans and Mobile. His army of about 32,000 men was four to six times the size of the original U.S. army. Furthermore, Mexican troops were well armed, disciplined, and, above all, experienced in scores of revolutions. Parades also counted on logistics. The principal theater of war would be Texas, hundreds of miles from the populous areas of the United States. Many Centralists believed that abolitionists' objections to the war would demoralize the United States, and some Centralists believed a Mexican invasion would be supported by a massive slave uprising.
Thus, the quick defeats at Palo Alto and Resaca de la Palma surprised and shocked the Mexican leadership. The U.S. victories against a larger, better trained force were attributed to the unexpected effectiveness of the American light artillery. Parades found it expedient, however, to lay the blame on his commanding general, and he quickly replaced him. The Mexican garrison evacuated Matamoros, moving to the south.
Taylor's Delay
Taylor occupied Matamoros on May 18 but then delayed for several months before moving south. He was apparently waiting for transportation promised him by the U.S. government, though his critics branded him inept. In July he moved his base up the Rio Grande to Camargo, but it was only in August that Taylor began planning the attack on Monterrey.
By that time American strength on the Rio Grande had swollen to nearly 20,000 troops, nearly all volunteers. The principal military problem was logistical support of such a quickly expanded force. The Americans were susceptible to subtropical diseases and found it difficult to maintain sanitary conditions in the camps. Fevers, dysentery, and general debility were rampant, and the mortality rate from sickness was alarming. A determined Mexican attack in July or August would have proven disastrous to the Americans.
Mexican Rebellion
The Mexicans did not attack because the Centralist government was collapsing. Rather than uniting Mexico, the war had given the Federalist faction an opportunity to rebel. Even while Taylor had been camped on the Nueces in the fall of 1845, a few Federalist leaders had been in contact with him, promising supplies and asking for assistance in overthrowing Parades. Northern Mexico was almost a Federalist stronghold, and as Taylor moved to the Rio Grande, he received increasing support from the rebels.
The defeats of the Centralist forces at Palo Alto and Resaca de la Palma precipitated open Federalist rebellions throughout Mexico. Major outbreaks at Acapulco and Guadalajara in July were followed by the defection of the military garrison of Veracruz on August 3 and that of Mexico City on August 4. Mexico was in turmoil.
On July 28, Parades turned the government over to his vice-president and went into hiding. The Centralists' government fell completely with the resignation of the vice-president on August 6. On August 22 the Federalists solemnly restored the constitution of 1824, and Valentin Gomez Farias, who had been deposed as vice-president by the Centralists in 1834, assumed temporary control of the government as the nation's only legitimate official.
In the meantime, Santa Anna had returned to Mexico. Having promised President Polk that he would work to effect a truce, he was allowed to pass through the U.S. naval blockade and land at Veracruz on August 16. Talk of a truce was forgotten. Perhaps the only leader capable of uniting the nation, he soon received command of the Mexican army; in December he was elected president by the Mexican Congress but did not formally assume office until the following March.
Monterrey and Buena Vista
In the meantime, Taylor began his advance on Monterrey. He reached that fortified town, which had a garrison of more than 10,000 troops, on September 19 and began his attack on the morning of September 21. With about 2,000 men, Gen. William J. Worth captured the road between Monterrey and Saltillo and by noon was storming Federation Hill. Six companies of Texas Rangers charged up the hill, seized the enemy artillery, and turned the cannon on retreating Mexican forces. On the opposite side of the city a diversionary attack penetrated the town, despite much confusion. On September 22 the Americans rested, but they resumed the attack the next day. After bloody street-to-street fighting, the Mexican general Pedro de Ampudia requested and was granted a truce. On September 25 he was permitted to withdraw his forces from the city, and an 8-week armistice was agreed upon. Total Mexican casualties were estimated at 367. The Americans had 368 wounded and 120 killed.
Taylor was criticized both by the military and by President Polk for agreeing to an armistice. Taylor therefore informed Santa Anna, who had assumed command of the Mexican forces at San Luis Potosi, that the armistice would be terminated early. On November 16 he occupied Saltillo. His position was strengthened by an independent force under Gen. John E. Wood, which took Parras, to the west of Monterrey, on December 5.
In January 1847, Santa Anna moved north with about 20,000 men to dislodge Taylor. Dispatches captured by the Mexicans had revealed that most of Taylor's forces were being withdrawn to take part in Gen. Winfield Scott's proposed landing at Veracruz. Word of Santa Anna's approach reached Taylor on February 21, and although outnumbered almost three-to-one, he took up a position at the hacienda of Buena Vista, a few miles from Saltillo. The Mexican attack began on February 22, when troops led by Ampudia gained an advantage and forced the Americans to abandon important defensive positions. The next morning the main Mexican force nearly overcame the U.S. defense. However, a dramatic charge led by Col. Jefferson Davis about noon and a determined artillery advance under Capt. Braxton Bragg finally saved the day for the Americans. Their casualties numbered about 700, but the Mexican losses were about 1,800. Santa Anna withdrew that night and moved south to intercept Scott's invasionary force. No further fighting occurred in northern Mexico, but Taylor remained in command of a small force there until he returned to the United States in November 1847.