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Mexican-American War
Battle of Churubusco.jpgZachary Taylor political cartoon.jpgBattle of Reseca de la Palma.jpgBombardment of Veracruz.jpg
Clockwise from top left: The Americans winning the Battle of Churubusco outside Mexico City; a political cartoon criticizing Whig candidate Zachary Taylor for his involvement in the war; a depiction of the U.S. bombardment of Veracruz; U.S. soldiers pursuing retreating Mexican troops in the Battle of Reseca de la Palma.
Date April 25, 1846 – February 2, 1848

(1 year, 9 months, 1 week and 1 day)

Location Southwestern North America, Mexico
Result Decisive American victory
Bear flag digital.png California
Modern Burgundy (Pax Columbia)-1-.png Columbia
Flag of Brazoria.png Texas
Flag of the United States.svg United States
Indian tribes
Flag of the Comanche.svg Comanche
Flag of the Navajo.svg Navajo
Flag of the Centralist Republic of Mexico.svg Mexico
Flag of the Saint Patrick's Battalion.png St. Patrick's Battalion
Commanders and leaders
Flag of the United States.png James K. Polk
Flag of the United States.png Winfield Scott
Flag of the United States.png Zachary Taylor
Flag of the United States.png Stephen Watts Kearny
Flag of the United States.png John D. Sloat
Flag of the United States.png William J. Worth
Flag of the United States.png Robert F. Stockton
Flag of the United States.png Joseph Lane
Flag of the United States.png Franklin Pierce
Flag of the United States.pngDavid Conner
Flag of the United States.png Matthew C. Perry
Flag of the United States.png Thomas Childs
Bear flag digital.png John C. Fremont
Bear flag digital.png William B. Ide
Flag of Brazoria.png Garrett Hawke
Flag of Brazoria.png Sam Houston
Flag of Brazoria.png Mirabeau B. Lamar
Modern Burgundy (Pax Columbia)-1-.png Alexander I
Modern Burgundy (Pax Columbia)-1-.png Louis, Duke of Gaul
Modern Burgundy (Pax Columbia)-1-.png Boris Varennikova
Flag of the Centralist Republic of Mexico.svg Antonio López de Santa Anna
Flag of the Centralist Republic of Mexico.svg Mariano Arista
Flag of the Centralist Republic of Mexico.svgPedro de Ampudia
Flag of the Centralist Republic of Mexico.svg José María Flores
Flag of the Centralist Republic of Mexico.svg Mariano G. Vallejo
Flag of the Centralist Republic of Mexico.svg Nicolás Bravo
Flag of the Centralist Republic of Mexico.svg José Joaquín de Herrera
Flag of the Centralist Republic of Mexico.svg Andrés Pico
Flag of the Centralist Republic of Mexico.svg Manuel Armijo
Flag of the Centralist Republic of Mexico.svg Martin Perfecto de Cos
Flag of the Centralist Republic of Mexico.svg Pedro Maria de Anaya
Flag of the Centralist Republic of Mexico.svg Agustin Jeronimo de Iturbide y Huarte
Flag of the Centralist Republic of Mexico.svg Joaquín Rea
1846: 10,000

1848: 42,000 soldiers
and marines
70,000 militia

c. 34,000–60,000 soldiers
Casualties and losses
2,384 killed in battle

14,511 total dead

c. 34,000–60,000 soldiers
a Later to become Sierra
b Later to become Brazoria

The Mexican-American War, also known as the Mexican War, the Western-Mexican War, the Invasion of Mexico, the War of American Aggression, or, in the case of the new republics, the War of Independence, was an armed conflict between the United States and its allies, Texas and California against the Centralist Republic of Mexico (which during the war, became known as the Second Federal Republic of Mexico) and the Wabash Confederation that lasted from 1846 to 1848.

Lasting for more than a year and a half, the war was the fourth instance in American history where a war was fought on American soil. American and Texan forces led an expedition in New Mexico, heading southward into the Mexican homeland. On the California front, American and Californian forces fought scattered battles throughout the Southwest to disperse Mexican forces, eventually pressing southward into the Baja California peninsula. By the summer of 1847, pro-American forces were deep in Mexico, adding more pressure to Mexico following the capture and occupation of Veracruz, a strategic port city in the Gulf of Mexico. Following the capture of Mexico City by American forces the fall that year, the Treaty of Guadalupe Hidalgo concluded the war, forcing Mexico to allow the placement of American troops and creation of overseas bases. The treaty also officiated the independence claims of California and Texas, which would both later become Sierra and Brazoria respectively.


Symbols of Sierra.png
Part of a series on the
History of Sierra
Early Native Sierrans
European exploration
Portolà expedition
Spanish mission system
Las Californias
Mexican War of Independence
California Trail
Mexican-American War
California Republic
Gold Rush
1858 Constitution
Sierran Civil War
War of Contingency
Second Industrial Revolution
Progressive Era
Sierran Cultural Revolution
World War I
Great Depression
World War II
1950 Charter
Great Basin controversy/Cross-Pacific affair
Cold War
The Disturbances
Contemporary era
Global War on Terrorism
Baja California crisis
Second Cold War
Abdication of Smith II
Assassination of Steven Hong
2017 Pawnee earthquake

Mexico, having secured its independence from Spain in 1821, was politically unstable and on the verge of a full-blown civil war. As Americans began settling the Mexican colonies of California and Texas, the Mexican government grew increasingly agitated and wary. The American settlers, largely ignoring Mexican customs and law, were viewed as unwelcome and seen as a threat to the integrity of the Mexican nation. In addition, frequent attacks and raids made by Indian tribes, particularly from the Comanche, Apache, and Navajo, compounded the weakness of Mexican control over its northern territories. The Indians themselves stole thousands of cattle for their own use and to trade with the expanding American market.

In 1835, the Texas Revolution erupted, following the imprisonment of Texan leader Stephen F. Austin and the introduction of unpopular legislation in Texas by Antonio López de Santa Anna. The Revolution resulted with the Texan rebels victorious forcing the Mexican government to sign the Treaties of Velasco, thereby granting Texas independence. The Mexican government however, continued to refuse to recognize Texan independence by never ratifying the treaty.


While Texas became de facto independent following the signage of the Treaties of Velasco, Mexico refused to recognize Texas. However, major foreign powers including the United States and Albion-Gaul which chose to recognize Texas, strongly advised the Mexican government to refrain from reconquering Texas. A major source of contention was the fact that the treaty did not define an official boundary between Texas and Mexico. Texas claimed all lands up to the Rio Grande while Mexico asserted that it was further north, at the Nueces River.

In California, more and more Americans were settling in the Mexican territory, ignoring local law and custom as their Texan counterparts. Following the Oregon Trail, American settlers arrived in the hopes of pursuing economic opportunity and exercising personal liberty. The idea of manifest destiny was also carried along, with Americans treating California as American soil, a concept met with alarm by the Mexican government. Viewed with suspicion and resentment, the Mexican government attempted to deport Americans whom they believed to be disorderly.

Californian-born Mexicans on the other hand, known as Californios, were Mexican citizens by birth. Although treated as first-class citizens compared to their Anglo neighbors, the Californios grew increasingly dissatisfied with the Mexican government over land use, local policy, and miscommunication. California, having always been largely autonomous and thousands of miles from the inefficient government in Mexico City, saw little use in remaining a part of a dysfunctional Mexico. As Anglo-speaking settlers and Californios began banding together in support of independence, the Mexican government tried tightening its control by arresting and even executing known dissidents.

Mexico itself, reeling in from its disastrous defeat in the Pastry War, continued to suffer political infighting from several rival factions. Unstable, and unable to effectively execute authority in its northern territories, Mexico had a severe military and diplomatic deficit which the United States and its allies would capitalize on during the war.

In the United States, the issue of slavery and expansionism was driving the country apart. With sectionalism on the rise, the threat of Southern secession and even a civil war was looming. Democrats, particularly those in the South, strongly supported expanding American territory westward, which would include the Mexican territories of Texas and California. On the other hand, the Whigs opposed expansion and a war with Mexico.

On April 25, 1846, a Texan force led by military official Seth Thornton marched toward the Rio Grande in hopes of establishing a military post. He and his men were ambushed by Mexican troops, who greatly outnumbered then, and resulted in 17 casualties, 11 of which were deaths, and 49 captures including Thornton himself. The incident, come to be known as the Thornton Affair, angered Texans and Americans who heard the news. Ready to declare war, the Texan government formally asked the American government for military support and assistance.

With word finally reaching to Washington, President James K. Polk presented the issue to Congress on May 11, 1846, which viewed the affair an attack against the American people. Two days later, on May 13, Congress jointly declared war with the Texan Congress on Mexico. On July 7, just a little less than a month later, Mexico formally recognized hostilities with the United States and declared war.


The painting War News from Mexico (1848) depicts Americans reacting to news from the war front.

Following the United States' declaration of war on May 13, 1846, American forces crossed the Mexican border and formed two main invasion fronts. The invasion effort in Western Mexico was Stephen W. Kearny with the help of a Pacific fleet led by John D. Sloat. In California, the rebels were led under the direction of American captain John C. Fremont whose objective was to expel Mexican authorities and troops from the area. American officers John E. Wool and Zachary Taylor along with Texan general Garrett Hawke, on the other hand, were given direct orders to occupy Mexico and march as far south as the city of Monterrey.

California Campaign

Due to the long distance from Washington to California, news of the declaration of war took three months to reach the American community. Despite this, the American immigrants and Californios had already begun an act of rebellion, attacking Mexican government buildings and defying authorities. On June 14, 1846, over 100 Americans and 50 Californios seized control of an unprotected Mexican government outpost in the city of Sonoma. Known as the Bear Flag Revolt, the rebels, who called themselves the "Bear Flaggers", flew the Bear Flag and proclaimed the independence of California from Mexico as the "California Republic". Within a week of the attack, over 200 more civilians joined in defending the fort and news of the capture inspired several more seizures throughout California.

Pío Pico, governor of Alta California, the chief Mexican official over the land, declared the territory in a state of emergency and requested assistance from Mexico City. Giving orders to capture or kill any rebels, Pico placed military operations to his most senior military official, José Castro. Castro, mobilizing his troops, prioritized in protecting Monterey, the capital of Alta California, and the immediate vicinity. In Porciúncula, the rebellion was quashed and as much as 30 rebels, of American, Britannian, and Mexican nationality, were executed under the orders of Captain Luis Gutierrez on June 21.

The original Bear Flag raised by the Bear Flaggers in Sonoma.

On June 25, John C. Fremont arrived to San Francisco City, then known as Yerba Buena, where the city was under the control of the Bear Flaggers. Setting up a provisional capital for the new California Republic, Fremont renounced his U.S. citizenship and accepted the title and position of general of the California military.

Commodore John D. Sloat, commander of the U.S. Navy's Pacific Squadron, stationed in Mazatlan, Mexico, was given orders to capture San Francisco Bay and other strategic Californian bays should war break out. Setting sail for Monterey, Sloat reached the city on July 1, ordered his troops to capture the city. Pico, caught aback from Sloat's arrival, immediately surrendered and was placed under house arrest at the Governor's Mansion. The capital of Alta California was captured by Sloat without having a single bullet fired within a day. News of this capture boosted morale on the Californian front and inspired defections from the Mexican military to the Californians and Americans, greatly improving the Californians' efforts in the region. Sloat, who originally wanted to raise an American flag over Monterey, assented to raising the Californian flag, as a gesture of recognition for Californian independence.

Following Sloat's capture in Monterey, Sloat transferred his duties to Commodore Robert F. Stockton who pursued a more aggressive military strategy. Stockton ordered Fremont, who had arrived from San Francisco City, to move to San Diego so he would be in position to attack Porciúncula. By the time Fremont arrived in San Diego, Stockton landed in San Pedro and captured the city of Porciúncula unopposed by the Mexican military. Mexican captain Luis Gutierrez, who had control over Porciúncula, fled for Sonora but was captured en route to Mexico just outside the city. Captured, Stockton had Gutierrez tried and convicted for the execution of the 30 plus men killed on Gutierrez' orders. Gutierrez was executed by fire squad on July 3 and news of death served as a warning for any Mexican troops who dared oppose Stockton. A counterinsurgency of 250 Californios led by José María Flores, who acted independently from the orders of the Mexican government, unsuccessfully tried to expel Stockton from the city. Defeated, Stockton had Flores and his men detained and forced to do manual labor.

Stockton received reinforcements of 200 men under the command of U.S. Captain William Mervine soon after this victory and combined forces to fight off the Mexicans in the one-hour long Battle of Dominguez Rancho on October 8. Despite suffering only 4 casualties, Mervine's men were defeated and he was forced to retreat to the sea. In November, American and Brazorian troops under the command of General Stephen W. Kearny finally arrived from the east, crossing the Colorado River, and into California. With 100 dragoons, Kerany and his men fought in the Battle of San Pascual where they were ill-prepared for the fight and completely overwhelmed by the Mexican forces. The battle resulted in 18 dead and 13 wounded, making it the worst engagement for the Americans in the California campaign. Shortly afterward, Kearny's troops met with Stockton's 1,200-strong army where they marched back to the site of the failed battle of San Pascual and eliminated the final stronghold of pro-centralist Mexican troops.

The Mexican government in California was forced to sign the Treaty of Cahuenga on January 13, 1817 which put an end to all hostilities in Alta California. It however, did not grant independence to California as the Californians had hoped. As it was not a formal treaty between Mexico, California, and the United States, the Californians would not receive independence until the signage of the Treaty of Guadalupe Hidalgo a year later. In the meantime, Stockton and Kearny, under the flag of the American government, agreed to continue protecting the Californians from any future, potential attacks under the pretense that it would respect California's sovereignty and soon-independence.

Texas Campaign

Mexico Campaign

March to Mexico City

Seizure of Veracruz

Capture of Mexico City

American-Hoosier War

Final operations

Treaty of Guadalupe Hidalgo


Independence of Brazoria

Independence of California

See also

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