Mexican-American War
The Mexican-American War lasted from 1846 to 1848 and resulted in Mexico losing 55% of its territory. To understand why this war began, we need to delve into the political and social climate of the early 19th century.
The Mexican-American War officially began on April 25, 1846.
The seeds of conflict were sown years earlier, with rising tensions over territorial claims. At the heart of the dispute was the region now known as Texas, which became a critical battleground between the two nations.
While the U.S. was motivated by Manifest Destiny, Mexico was struggling to maintain control over its vast northern territories. Politically unstable and militarily weaker than the U.S., Mexico was unprepared for the conflict.
The Mexican-American War began in a climate of rising tension, fueled by U.S. territorial ambitions and Mexico’s struggle to defend its sovereignty. What started as a border dispute quickly escalated into a full-scale war.
The Mexican-American War was fought on multiple fronts, from Texas to California to Mexico’s heartland. What began as a border skirmish quickly escalated into a large-scale conflict involving significant battles and territorial conquests.
The U.S. gained over 500,000 square miles of Mexican territory.
Mexico lost about half of its territory, including valuable land in what is now the U.S. Southwest. This loss severely weakened the country economically and politically, and it took decades for Mexico to recover.
How Did the Mexican-American War Begin?
The roots of the war can be traced to the early 1800s, particularly around the issue of Texas. Originally part of Mexico, Texas was sparsely populated and its remote location made it difficult for Mexico to govern effectively.
In the 1820s, Mexico encouraged U.S. settlers to migrate to Texas, hoping to develop the region’s economy. However, by the 1830s, the relationship between the Mexican government and these settlers began to sour.
Most Texas settlers were American and clashed with Mexico over issues like language, customs, and religion. More importantly, slavery was illegal in Mexico, but many American settlers in Texas were slaveholders.
These differences, coupled with Mexico’s centralist policies, prompted Texas to declare independence from Mexico in 1836. After a series of battles, Texas achieved its independence and became the Republic of Texas.
After nearly a decade as an independent republic, Texas was annexed by the USA, causing outrage in Mexico, which had never recognized Texas’ independence. The annexation set the stage for future military conflict.
Why Did the Mexican-American War Begin?
Several factors contributed to the outbreak of the Mexican-American War.
The primary cause was the U.S.’s desire for expansion, driven by the concept of Manifest Destiny – the belief that the USA was destined to expand its territory across North America, from the Atlantic to the Pacific Ocean.
This expansionist mindset encouraged American policymakers to seek new lands, including Texas and the territories of New Mexico and California, which were still part of Mexico.
The annexation of Texas reignited the dispute over where the U.S.-Mexico border lay. The USA claimed that the border was the Rio Grande River, while Mexico insisted that the border was further north, along the Nueces River.
Diplomatic attempts to resolve the disagreement failed. President James K. Polk sent an envoy to negotiate the purchase of California and New Mexico. Mexico, unwilling to sell its northern territories, rejected the proposal.
In 1846, President James K. Polk, a staunch supporter of expansionism, sent U.S. troops into the disputed territory between the Rio Grande and Nueces rivers. On April 25, Mexican forces attacked a U.S. patrol, leading Polk to call for war.
Key Campaigns and Battles (1846–1848)
The Start of the War (April 1846)
The war began after a border skirmish forces on April 25, 1846.
Mexican troops attacked U.S. soldiers, triggering the official start of hostilities. The U.S. saw this as an attack on its soil, prompting President James K. Polk to ask Congress to declare war, which they did on May 13, 1846.
The Northern Mexico Campaign (1846)
Battle of Palo Alto (May 8, 1846): The first major battle of the war took place just north of the Rio Grande. U.S. General Zachary Taylor’s forces defeated a larger Mexican army under General Mariano Arista. This battle set the tone for future U.S. victories.
Battle of Resaca de la Palma (May 9, 1846): A day later, Taylor’s forces attacked the retreating Mexican army in Texas, again achieving a decisive victory. These early victories gave the U.S. control of the disputed border region and allowed them to move further south.
Siege of Monterrey (September 21–24, 1846): Taylor’s army captured the heavily fortified city of Monterrey in northeastern Mexico after intense urban combat. Following the surrender of the Mexican garrison, a temporary armistice was declared, though it was soon broken as hostilities continued.
The California Campaign (1846–1847)
Bear Flag Revolt (June 1846): The war in California started before official U.S. troops arrived. American settlers in Mexican-controlled California launched the Bear Flag Revolt, declaring independence from Mexico.
This rebellion was swiftly backed by U.S. Navy forces under Commodore John D. Sloat, who occupied Monterey, California.
The capture of Los Angeles (August 1846): U.S. forces took control of Los Angeles, but local Mexican forces, along with California residents, later staged a revolt to briefly regain the city.
Battle of San Gabriel (January 8-9, 1847): U.S. forces under General Stephen Kearny and Commodore Robert Stockton decisively defeated Mexican forces near Los Angeles, ending resistance in California.
The New Mexico Campaign (August 1846)
Capture of Santa Fe (August 18, 1846): U.S. forces, led by Colonel Stephen W. Kearny, marched into Santa Fe (modern-day New Mexico) without facing any significant resistance. Kearny’s Army of the West was tasked with securing New Mexico and then moving on to California.
The Central Mexico Campaign (1847–1848)
Battle of Buena Vista (February 22–23, 1847): As General Taylor moved deeper into Mexico, his forces encountered General Antonio López de Santa Anna, the Mexican president and military leader, near the city of Buena Vista.
Despite being heavily outnumbered, Taylor’s well-positioned troops repelled the Mexican attacks. The Mexican army withdrew, marking a major turning point in the war.
Siege of Veracruz (March 9–29, 1847): U.S. General Winfield Scott led an amphibious landing at the Mexican coastal city of Veracruz, the largest such operation in history at that point. After a prolonged siege, the U.S. captured Veracruz, opening the way to Mexico City.
Battle of Cerro Gordo (April 18, 1847): Scott’s army moved inland, defeating a Mexican force commanded by Santa Anna at Cerro Gordo, a fortified position in the mountains. This victory allowed Scott to continue his advance toward Mexico’s capital.
The capture of Mexico City (September 13, 1847): After a series of battles at Contreras, Churubusco, and Molino del Rey, Scott’s forces reached the outskirts of Mexico City.
The climactic Battle of Chapultepec on September 12–13 saw U.S. forces storm the heavily fortified Chapultepec Castle, a symbol of Mexican resistance. After capturing the castle, U.S. forces entered Mexico City, effectively ending the war.
Treaty of Guadalupe Hidalgo (February 2, 1848)
The war officially ended with the signing of the Treaty of Guadalupe Hidalgo on February 2, 1848. Under the treaty:
Mexico ceded California, New Mexico, and other parts of the modern-day southwestern U.S. (including Arizona, Nevada, Utah, and parts of Colorado and Wyoming) to the United States. The U.S. agreed to pay Mexico $15 million for the ceded territories.
The Rio Grande was established as the official U.S.-Mexico border, confirming U.S. control over Texas.
Impact of the Mexican-American War
The Mexican-American War was fought on multiple fronts, from Texas to California to Mexico’s heartland. What began as a border skirmish quickly escalated into a large-scale conflict involving significant battles and territorial conquests.
The U.S. gained over 500,000 square miles of Mexican territory.
Mexico lost about half of its territory, including valuable land in what is now the U.S. Southwest. This loss severely weakened the country economically and politically, and it took decades for Mexico to recover.
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