Mexican-American War 1846-1848

The Mexican-American War between the United States and Mexico developed from the American annexation of Texas in 1845 and the resulting dispute over whether Texas ended at the Nueces River (Mexican claim) or the Rio Grande (U.S. claim). The war – in which US military forces were consistently victorious – resulted in American acquisition of more than 500,000 square miles (1,300,000 square km) of Mexican territory extending westward from the Rio Grande to the Pacific Ocean.

Mexico severed relations with the United States in March 1845, shortly after the US annexation of Texas. In September US President Polk sent a secret mission to Mexico City to negotiate the disputed Texas border, settle American claims against Mexico, and purchase New Mexico and California for up to $30,000,000. Mexican officials, aware in advance of American intentions, refused to receive the mission. In January 1846, American troops occupied the disputed area between the Nueces and the Rio Grande.

On April 25, 1846, Mexican troops crossed the Rio Grande and attacked the American troops in the disputed territory, killing or injuring 16 of them. The American administration, already bellicose on the grounds of Mexican refusal to pay US claims or negotiate, now claimed that Mexico had "invaded our territory and shed American blood on American soil." The US Congress approved a declaration of war on May 13, 1846 although political divisions were evident.

Congress overwhelmingly approved a declaration of war on May 13, but the United States entered the war divided. Democrats, especially those in the Southwest, strongly favoured the conflict. Most Whigs viewed Polk's motives as conscienceless land grabbing. And Abolitionists saw the war as an attempt by the slave states to extend slavery and enhance their power when additional slave states were created out of the soon-to-be-acquired Mexican lands.

Following its original plan for the war, the United States sent its army on the Rio Grande south to invade Mexico while a secondary force was to occupy the Mexican states of New Mexico and California. The campaign into New Mexico and California encountered little resistance and the residents appeared to accept American occupation with a minimum of resentment. Meanwhile, American army advancing south fought several battles below the Rio Grande, captured the important city of Monterrey, and defeated a major Mexican force at the Battle of Buena Vista in February 1847. The American army advancing south routinely failed to aggressively pursue Mexican forces after defeating them.

The American leadership (impatient with the progress of the advance south), revised the war plan, ordering the deployment of an army by sea to capture the port of Veracruz and march inland to Mexico City. Veracruz was occupied in March 1847, after a siege of three weeks and the army began the march to Mexico City. Despite substantial Mexican resistance, the American campaign was marked by an unbroken series of victories, and American forces entered Mexico City on Sept. 14, 1847. The fall of the Mexican capital ended the formal resistance of the Mexican armed forces. However, there was a great deal of Mexican guerrilla resistance and American counterinsurgency operations in the following months.

While the American intention was to secure a peace treaty immediately after the occupation of Mexico City this proved unrealistic; there was a long delay resulting from the difficulty of forming a new Mexican government capable of engaging in negotiations. On February 2, 1848, the Treaty of Guadalupe Hidalgo was signed by representatives of Mexico and the United States. Mexico was then required to relinquish its territories of New Mexico and Upper California (the present-day American states of California, Nevada, Utah, and parts of Arizona, New Mexico, Colorado, and Wyoming) for $15,000,000 while the United States agreed to assume more than US$3 million in claims from private citizens of these areas against the Mexican government.

For Americans, the war reopened the issue of extending slave holding into new territories, which had been largely dormant since the Missouri Compromise; the status of slavery in the newly acquired lands was eventually settled by the Compromise of 1850. For Mexicans, the territorial losses and the brief but traumatic occupation of Mexico City by United States troops engendered a deep-seated mistrust of the United States that still resonates in Mexican popular culture.

References

Clodfelter, 431-434; EB - Mexican War; COW7; Mallett, 125-126; Mexico - A Country Study; .

Derek R Mallett. Casualties Mexico; Casualties United States. Spencer C Tucker. Editor. The Encyclopedia of the Mexican-American War: A Political, Social, and Military History. Volume One (A-L). 2012.

Category

Inter-State War

Region

North America, Central America

Belligerents

Mexico, USA

Dispute

Territory

Initiation Date

April 25, 1846

Termination Date

February 2, 1848

Duration

1 year, 9 months, 9 days
(649 days)

Outcome

Imposed Settlement
(USA victory)

Fatalities

Total: 29,000
Military: 28,000
Civilian: 1,000

Mexico: 16,000
Military: 15,000
Civilian: 1,000

USA: 13,000
Military: 13,000
Civilian: 0

Magnitude

4.5