<P> The Mexican -- American War , also known as the Mexican War in the United States and in Mexico as the American intervention in Mexico , was an armed conflict between the United States of America and the United Mexican States ( Mexico ) from 1846 to 1848 . It followed in the wake of the 1845 American annexation of the independent Republic of Texas . Mexico had considerable instability under the caudillo leadership of President / General Antonio López de Santa Anna , with many constitutional changes leading up to the conflict . Mexico still considered Texas to be its northeastern province and a part of its territory , and did not recognize the Republic of Texas , which had seceded from Mexico in the 1836 Texas Revolution a decade earlier . In 1845 , newly elected U.S. President James K. Polk sent troops to the disputed area , and a diplomatic mission to Mexico . After Mexican forces attacked American forces , Polk cited this in his request that Congress declare war . </P>
<P> The Mexican -- American War , also known as the Mexican War in the United States and in Mexico as the American intervention in Mexico , was an armed conflict between the United States of America and the United Mexican States ( Mexico ) from 1846 to 1848 . It followed in the wake of the 1845 American annexation of the independent Republic of Texas . Mexico had considerable instability under the caudillo leadership of President / General Antonio López de Santa Anna , with many constitutional changes leading up to the conflict . Mexico still considered Texas to be its northeastern province and a part of its territory , and did not recognize the Republic of Texas , which had seceded from Mexico in the 1836 Texas Revolution a decade earlier . In 1845 , newly elected U.S. President James K. Polk sent troops to the disputed area , and a diplomatic mission to Mexico . After Mexican forces attacked American forces , Polk cited this in his request that Congress declare war . </P>
the united states gained control of texas after armed conflict with the forces of
the united states gained control of texas after armed conflict with the forces of
Mexico
Mexico