There are too many American settlers here! They are taking over our land!
We need to fulfill Manifest Destiny. I want all of the Southwest territories of Mexico! I want California!
I will ask Congress to declare war if my plan works.
Cross the Nueces River with your regiment and provoke a Mexican attack.
American were settling in Texas. They were growing and expanding which soon angered the Mexicans and led to the war.
“Grasping ambition, tyrannic usurpation, atrocious aggression, cruel and haughty pride, spread, and pervade the land.”
People like James K. Polk and Zachary Taylor supported the war. Polk believed in Manifest Destiny and wanted to take the remaining Southwest territories from Mexico, including California.
"Now, boldly and continually to denounce the war... as you can easily imagine, subjects us to great odium, and brings down upon our heads the heavy charge of “treason” and “traitors to the country.” But our testimony is not in vain. It burns like fire upon the national conscience."
Polk sent Zachary Taylor to provoke a Mexican attack. When he was told that his plan worked, Polk asked Congress to declare war, and they did.
Mexico has surrendered! All of their territories are ours!
However, there were some Americans who were against the war, such as Frederick Douglass. He saw and expressed that violence and conflict were on people's minds and that people were being enslaved.
William Lloyd Garrison was among the people who were opposed to the war. He said that even though them denouncing the war brought down the charge of treason on them, their testimony was not for nothing.
As a result of the war, the Americans won and the Mexicans agreed to give up and sell the Mexican Cession.