Mexican-American War

The physical beginning of the Mexican-American war between the United States and Mexico began with a Mexican attack on American troops who were stationed on the southern border of Texas on April 25, 1846. The swift conclusion to the war took place as General Winfield Scott occupied the Mexican capitol city, Mexico City on September 14, 1847. Within a few months, the Treaty of Guadalupe was signed with Mexico recognizing the US annexation of Texas as well as Mexico succeeding from California and New Mexico. 1 The causes of the Mexican-American war varies from historian to historian.
Some blame a dictatorial Centralist government of Mexico beginning the war by continuing to claim Texas even after its establishment of an independent republic. Others argue the United States provoked war with Mexico by annexing Texas as well as stationing troops at the Mexican border. A final thought is that the greed of United States President James Polk who “forced Mexico to war in order to seize California and the Southwest”. 2 The most likely cause of the Mexican-American War is a combination of the three.
The government of Mexico leading up to and during the Mexican-American was an unstable, dictatorial, Centralist government. Dictator Antonio Lopez de Santa Anna was a Centralist, who supported an autocratic government and ran Mexico as such. This led to various rebellions and insurgencies within Mexico itself. In 1836, after Mexico had won its independence from Spain, Texas rebelled against the government of Mexico. With assistance from the US, Texas was able to win its independence from Mexico. However, stubbornly the Mexican government refused to recognize the new Republic of Texas. This stubbornness also continued into the distant northern provinces of California and New Mexico that remained sparsely settled and had a Spanish speaking population of only 75,000 in 1840. 4 Mexican officials vowed to preserve their historic boundaries, “so when the Texas constitution convention voted on July 4, 1845 to enter the American Union, Mexico broke off diplomatic relations with the United States”. 5 Breaking off of diplomatic relations could have been a direct cause of the Mexican-American War.

Another direct cause of the Mexican-American war was the provoking done by the United States through annexing Texas as well as stationing troops on the southern border of Texas. The US annexation of Texas, by a joint congressional resolution had caused considerable political debate in the United States. 6 The Independent Republic of Texas had tried to join the United States for several years, yet was blocked by antislavery forces that feared several new slave states would be created from the Texas territory. Upon British interest in independent Texas, the administration of John Tyler began to take action as anti-British feeling was behind most of the expansionist policy statements of the United States.
8 Afterwards when James Polk took Presidency, he set in motion his plans to acquire Mexico’s northern provinces. His plan involved sending down General Zachary Taylor and an American army to occupy the Rio Grande, which was the Republic of Texas’s claimed border from Mexico. Ulysses S. Grant, who was a young officer under Taylor was quoted “We were sent to provoke a fight but it was essential that Mexico should commence it”. 9 When the armies finally clashed, Polk delivered his war message declaring Mexico “has passed the boundary of the United States, has invaded our territory, and shed American blood upon the American soil”. 10 Very clearly, the annexation of Texas and provoking of confrontation near Mexico’s border was a direct influence on the Mexican-American War.
A final thought is that the greed of United States President James Polk forced Mexico to war in order to seize California and the Southwest. The acquisition of Texas fueled President Polk’s appetite to fulfill “Manifest Destiny” with the possibility of acquiring all the Mexican lands between Texas and the Pacific Ocean. 11 Polk sent John Slidell to Mexico in December of 1845 in order to secure the Rio Grande boundary and to purchase California and New Mexico for $30 million dollars.
Arguing that the annexation of Texas was illegal, the Mexican government refused Slidell’s offer expressing the purchase of New Mexico and California was not an option. 12 Understanding that the acquisition of these new provinces wasn’t going to take place diplomatically, Polk was willing to utilize the United States military forces if necessary. Polk’s hastiness in going to war with Mexico introduced free-state, slave-state controversy. Northerners opposed the war all together expressing that Polk didn’t have the United States best interests at heart.
Many Southerners on the other hand were in favor of expansion and supported slavery. Overall Manifest Destiny was an idea implemented during this time period to justify the movement westward and the seizing of the southwest. President Polk’s greed for California and New Mexico definitely was a cause of the Mexican-American war. Ironically enough, these three causes of the Mexican-American war helped drive separation in the United States of America even leading to possible causes of the American Civil War.
When General Winfield Scott occupied Mexico City bringing an end to the war and the Treaty of Guadalupe was signed, the United States was successful at gaining California, New Mexico as well as Texas. The causes of the Mexican-American War leading up to this conclusion though are apparent as well. A dictatorial Centralist government of Mexico, United States provoking war through annexing Texas and stationing troops on the southern border as well as a President’s greed for California and the Southwest all played contributing factors in the Mexican-American War.