Why did the US invade Mexico in 1846?

The US invaded Mexico in 1846 to assert its claim on the Rio Grande border, and also in the hopes of seizing New Mexico and Alta California from Mexico.

Who led the armies in the Mexican-American War?

During the Mexican-American War, the US armies were commanded by Zachary Taylor and Winfield Scott. The Mexican armies were led by Mariano Arista and Antonio López de Santa Anna, among others.

When did Mexico City fall to the US?

US General Winfield Scott entered Mexico City on 14 September 1847, effectively ending the fighting stage of the Mexican-American War.

Timeline: Mexican-American War

Definition

The Mexican-American War (1846-1848) was a conflict between the United States and Mexico, sparked by the US annexation of Texas in 1845. Hoping to seize even more territory from Mexico, US President James K. Polk (served 1845-1849) used the Texas dispute to provoke a war, precipitating the US invasions of California, New Mexico, and the Mexican heartland. After the fall of Mexico City in September 1847, the Mexican government relinquished 529,000 square miles of territory to the US in the Treaty of Guadalupe Hidalgo. The war has often been regarded as an unjust invasion, both by contemporaries and later historians, and would only inflame the sectional divisions in the US that would lead to the American Civil War (1861-1865).

More about: Mexican-American War

Timeline

27 Sep 1821
End of the Mexican War of Independence; Mexico wins its independence from Spain.
18 Aug 1824
Mexico enacts a statute allowing foreigners to acquire land in the country.
2 Oct 1835
The Texas Revolution begins.
23 Feb 1836 - 6 Mar 1836
Battle of the Alamo.
21 Apr 1836
The Battle of San Jacinto ends in a Texian victory and Santa Anna's capture; the Republic of Texas is established.
4 Mar 1845
James Knox Polk is inaugurated as the 11th President of the United States, having run on an expansionist platform.
29 Dec 1845
Texas joins the US as the 28th state.
28 Mar 1846
Gen. Zachary Taylor's Army of Occupation arrives on the Rio Grande to enforce the territorial claims of the US; starts to build Fort Texas.
24 Apr 1846
General Mariano Arista takes command of the Mexican forces at Matamoros, facing the US army.
25 Apr 1846
The Thornton Affair; a detachment of 70 US dragoons are attacked by Mexican cavalry. The Mexican-American War begins.
8 May 1846
Battle of Palo Alto. The armies of Taylor and Arista fight to a standstill.
9 May 1846
Battle of Resaca de la Palma. Arista is defeated and forced to retreat across the Rio Grande.
13 May 1846
US Congress declares war on Mexico.
18 May 1846
Taylor occupies Matamoros.
6 Aug 1846
Santa Anna returns to Mexico, later seizes power.
14 Aug 1846
A US Army under Gen. Stephen W. Kearny occupies Santa Fe, brings New Mexico under US control.
20 Sep 1846 - 24 Sep 1846
Battle of Monterrey. The Mexican army agrees to evacuate Monterrey in exchange for the city's surrender to Taylor.
22 Feb 1847 - 23 Feb 1847
Battle of Buena Vista results in a US victory.
9 Mar 1847
A US army under Gen. Winfield Scott lands at Varacruz.
20 Aug 1847
Battle of Churubusco between Scott and Santa Anna. US victory.
8 Sep 1847
Battle of Molino del Rey. US victory.
12 Sep 1847 - 13 Sep 1847
Battle of Chapultepec. US victory.
14 Sep 1847
Fall of Mexico City to US forces.
2 Feb 1848
The Treaty of Guadalupe Hidalgo is signed, ending the Mexican-American War.