Mexican-American War

Part of the Expansion of the United States (1846–1848)

Date: April 25, 1846 – February 2, 1848[]

Location: Texas, Mexico, California, New Mexico, Arizona[]

Result: Decisive U.S. victory[]

Treaty of Guadalupe Hidalgo
Mexican Cession of California, Nevada, Utah, and parts of Arizona, New Mexico, Colorado, and Wyoming to the United States
U.S. recognition of the Rio Grande as the Texas border

Background[]

The Mexican-American War was a conflict between the United States and Mexico, primarily over territorial disputes in Texas and the American desire for westward expansion. After Texas won its independence from Mexico in 1836, tensions simmered for nearly a decade before erupting into war in 1846.

U.S. President James K. Polk, a strong believer in Manifest Destiny, sought to annex not only Texas but also California and the territories in between. Mexico, however, refused to recognize Texas as part of the United States, particularly the Rio Grande as its southern border.

When Mexican troops clashed with U.S. forces along the Rio Grande on April 25, 1846, President Polk declared that Mexico had shed American blood on American soil, leading Congress to declare war on May 13, 1846.

Major Campaigns and Battles[]

Taylor’s Northern Campaign (1846–1847)[]

Under General Zachary Taylor, U.S. forces scored early victories, including:

Battle of Palo Alto (May 8, 1846) – Taylor’s artillery devastated the Mexican army.
Battle of Resaca de la Palma (May 9, 1846) – Taylor drove Mexican forces across the Rio Grande.
Battle of Monterrey (September 21–24, 1846) – A hard-fought urban battle that ended with a U.S. victory.

After securing northern Mexico, Taylor’s forces faced the Battle of Buena Vista (February 22–23, 1847), where he repelled a much larger Mexican army under General Santa Anna in one of the war’s most decisive engagements.

Scott’s Mexico City Campaign (1847)[]

While Taylor fought in the north, General Winfield Scott led an amphibious invasion of Veracruz, storming ashore on March 9, 1847 in what would become the first major amphibious assault in U.S. history. After capturing Veracruz, Scott advanced inland, winning:

Battle of Cerro Gordo (April 18, 1847) – A daring flanking maneuver shattered Mexican defenses.
Battle of Contreras and Churubusco (August 19–20, 1847) – American forces overran Mexico’s last major defensive lines before reaching the capital.
Battle of Chapultepec (September 12–13, 1847) – U.S. Marines stormed Chapultepec Castle, giving rise to the famous phrase “From the Halls of Montezuma.”

On September 14, 1847, Mexico City fell to American forces, effectively ending the war.

General Van Dorn’s Role in the War[]

Among the many young officers who gained experience in the Mexican-American War was Earl Van Dorn, who later became a Confederate general in the Civil War. Serving under General Scott, Van Dorn distinguished himself as a fearless cavalry officer, taking part in battles during the Mexico City Campaign. His combat experience in Mexico sharpened his skills in fast-moving, offensive operations, traits he would later apply as a Confederate cavalry leader during the Civil War.

Treaty of Guadalupe Hidalgo (1848)[]

With Mexico’s army in ruins and its capital occupied, negotiations led to the Treaty of Guadalupe Hidalgo, signed on February 2, 1848. Under its terms:

Mexico ceded nearly half of its territory to the United States, including California, Nevada, Utah, Arizona, and parts of New Mexico, Colorado, and Wyoming (the Mexican Cession).
The U.S. paid Mexico $15 million for the territory.
The Rio Grande was officially recognized as the Texas-Mexico border.

The treaty fulfilled America’s vision of Manifest Destiny, but it also sowed the seeds of future conflict, as debates over slavery in the newly acquired territories intensified tensions between the North and South, leading toward the Civil War.

Legacy and Impact[]

The Mexican-American War was a pivotal moment in U.S. history, shaping the nation's borders and setting the stage for future conflicts.

Future Civil War generals such as Ulysses S. Grant, Robert E. Lee, Earl Van Dorn, Jefferson Davis, and Stonewall Jackson all gained experience during the war.
The war solidified U.S. military dominance in North America.
It left a lasting impact on Mexican-American relations, with Mexico viewing it as a national humiliation.