United States-Mexico War

Brief History

Throughout the 1840s, expansionist John L. O'Sullivan, editor of the United States Magazine and Democratic Review, endorsed the policy of manifest destiny, declaring, "it is our manifest destiny to overspread the continent alloted by Providence." Since most Americans supported this belief, citizens settled in the Mexican territories of Texas, New Mexico, and California. As a result, in 1842, President Polk promised to annex these three territories in order to pervade the North American continent with American institutions and values. In order to acheive his annexation goals, President Polk encouraged a revolution in Mexico and the other territories.

Mexican-American War

In July 1845, President James Polk ordered General Zachary Taylor to station approximately 4,000 troops at Corpus Christi near the Nueces River. In addition, the President ordered the Navy to occupy California ports in preparation for war. Following these preemptive military measures, President Polk sent politician, John Slidell, to negotiate with Mexico in November 1845. Slidell only offered to compensate Mexico for claims against their government by United States citizens in return for marking the Rio Grande River as the official boundary between the two nations. Additionally, Polk authorized Slidell to purchase New Mexico and Upper California. However, the Mexican government refused to negotiate with Slidell, which forced him to withdraw. Since the negotiations between the United States and Mexico failed, in January 1846 President Polk ordered General Taylor to station his troops at the Rio Grande. A few months later, Talyor moved his troops to a position opposite the Mexican city of Matamoros. Since there was no military action for months, President Polk requested a declaration of war from Congress on May 9 1846, which accused Mexico of failing to receive Slidell. Although the President was manipulating the legislative branch, Congress overwhlemingly supported the war after learning that American forces were attacked near the Rio Grande on April 24, 1846; the United States officially declared war on May 13, 1846. Mexico declared war with the United States on May 23, 1846.

Following the declaration of war, the United States attacked Mexico on several fronts. The Mexican territories, New Mexico and Upper California were conquered within a year. In the summer of 1846, American Colonel Stephen W. Kearney's "Army of the West," occupied Santa Fe without any opposition. Following this American victory, Colonel Kearney and his troops journeyed to Upper California. In March 1847, Colonels Kearney and Doniphan occupied Chihuahua, California. Following the conquest of these two territories, the United States appointed an American governor; Charles Bent was appointed governor of New Mexico and Richard Mason was the interim governor of California.

The war in Mexico lasted approximately two years. By September 1846, General Taylor, nicknamed "Old Rough and Ready" forced the Mexicans across the Rio Grande and occupied Matamoros, Monterrey, Saltillo, and Victoria. On February 22, 1847, Mexican General Santa Anna was defeated in the Battle of Buena Vista. Meanwhile, President Polk ordered General Winfield Scott to begin an invasion of the Mexican heartland by occupying the port of Vera Cruz. Follwoing the occupation of Vera Cruz in March 1847, General Scott marched towards the capital, Mexico City. By late September 1847, General Scott invaded Mexico City after winning the battles of Cerro Gordo and Chapultepec.

Treaty of Guadalupe Hidalgo

The Treaty of Guadalupe Hidalgo was signed on February 2, 1848. The treaty granted the United States the Rio Grande boundary, present-day New Mexico, California, Nevada, Utah and sections of Colorado, Arizona, and Wyoming in return for 15 million dollars to the Mexican government and compensation for the complaints of American citizens in these territories. As a result of the treaty, approximately 80,000 Mexicans were forced to assimilate into the United States. Following the ratification of the treaty, the American negotiator, Nicholas Trist, reamarked, "Could those Mexicans have seen into my heart at that moment, they would have known that my feeling of shame as an American was far stronger than theirs could be as Mexicans. For though it would not have done for me to say so there, that was a thing for every right minded American to be ashamed of, and I was ashamed of it, most cordially ashamed of it." As conveyed in Trist's comments, the Treaty of Gaudalupe immensly humiliated the Mexicans since they were unable to protect their territorial integrity and lost a large portion of their nation.

Treaty of Guadalupe Hidalgo

American and Mexican Soldiers

The Mexican and American soldiers resided in unsanitary conditions. The soldiers endured heat, insects, dust, and disease. Most soldiers in the war actually died from epidemics rather than enemy fire. In addition, primitive medical care resulted in military casualties.

The United States possessed two military regimes during the Mexican-American War; the national standing Army or US Army and state militias. Soldiers in the US Army enlisted for a five year period and were overseen by officers commissioned by Congress. Although there were approximately 8,613 soldiers, only 5,500 men actively served in the US-Mexico War. Several of the officers were recent graduates of the United States Military Academy, including Ulysses S. Grant and Robert E. Lee, two primary generals in the upcoming Civil War. However, there was little interaction between officers and common soldiers, which resulted from the strict military hierarchy. On February 11, 1847 Congress created an additional ten regiments to the national Army to serve for the duration of the war.
Additionally, most privates, corporals, and seargants were foreign born since a majority of Anglo-Americans were skeptical of the low wages. Therefore, most Americans were volunteer citizen-soldiers who elected their own officers. However, due to the unreliability of these state militias, Congress authorized the training of 50,000 twelve-month volunteers.
There were approximately, 26,922 soldiers in the standing Army and 73, 260 volunteers that served during the war.

Contrary to the US Army, the Mexican Army consisted of approximately 18,882 permanent troops organized into twelve regiments. The standing Army was regionally dispersed into five military territories. During the war, Mexico enforced a draft to strengthen their regional armies; however, these conscripts were usually difficult to train. Although most Mexican troops were unprepared for war, General Mariano Arista's 5,200-man Army of the North were the most experienced soldiers and engaged in battles with General Zachary Taylor's Army of Occupation.
In addition, 10,493 active militiamen contributed to the war. Most Mexican soldiers resided in unsanitary conditions and frequently experienced hunger; however, wives and girlfriends accompanied the troops on their expeditions.

War Support

In the United States, the war was primarily supported by southern Democrats, anxious to gain slave states. Aprroximately 75,000 men enlisted in state militias in addition to the thousands of volunteers in the national Army. Many Americans already residing in the desired land had expected the United States to annex the territories. In addition, most citizens believed in manifest destiny and claimed that it was the United States' right and will of God to annex all territories on the North American continent.
On the other hand, Whigs united in opposition to "Mr. Polk's War." Most Whigs regarded the war as an attempt to expand the United States and acquire more slave states. The most outspoken individual against the war was Henry David Thoreau, author of Civil Disobedience, who was imprisoned for refusing to pay his taxes to a government involved in war.

In Mexico, most citizens supported the use of force since they regarded military activity as the only means to protect their territorial integrity.






"Our food is abominable; when you break a biscuit, you can see it move...The pork and bacon are of the same character..."
-Account from US soldier




"The war with Mexico was unnecessarily and unconstitutionally commenced by the President"
-Abraham Lincoln




"The principle of waging war against a neighboring people to compel them to sell their country, is not only dishonorable, but disgraceful and infamous"
-Congressman Alexander Stephens (GA)