Charismatic but ruthless general Antonio Lopéz de Santa Anna seizes power in Mexico City. He favors a centralized, authoritarian government which angers people as most people are in favor of autonomy.
Texans rebel against Mexican rule, they seize Mexican garrisons at Goliad and San Antonio. This leads to Texas declaring independence and becoming known as the Lone Star Republic.
Texas is home to 30,000 American settlers named Anglo-Texans.
Santa Anna attacks a small Texas garrison at the Alamo. He slaughters the Texans here and at Goliad. The slaughtered become martyrs to Texas independence.
Sam Houston tricks Santa Anna and eventually captures Santa Anna and 730 Mexicans at the Battle of San Jacinto. Santa Anna is forced into signing a treaty recognizing Texas independence. The Mexican government does not accept the treaty as it grants Texas lots of land.
James K. Polk is voted in as President because of his promises to obtain the Oregon territory and Texas. He does not keep his promise to obtain all of Oregon which angers Democrats.
Congress narrowly votes to annex Texas, which enters the Union as a slave state. The border dispute between Texas and Mexico is reignited.
American troops led by General Zachary Taylor clash with a Mexican patrol killing eleven. This allows Polk to declare war on Mexico, which Congress approves on May 13.
Polk compromises with the British and agrees to split the Oregon territory at the 49th parallel of latitude. Northern democrats feel betrayed by this action of compromising.
General Stephen W. Kearny conquers New Mexico. The US Navy helps settlers seize control of California . Kearny and Frémont join forces to bring all of California under American control.
Taylor leads army deeper into northern Mexico, seizing the city of Monterrey.
Santa Anna tries to retake Monterrey, but Taylor's small army defeats the Mexicans in this bloody battle.
The navy carries an american army to Veracruz where General Scott seizes the port. Scott then marches 200 miles to Mexico City where he faces great resistance at Chapultepec (a fortress above Mexico City) from defenders including six children.
General Scott captures Mexico City effectively ending the war in a thorough American victory.