October 2, 1835 - May 14, 1836, Texas Revolution.

April 25, 1846 – February 3, 1848, Mexican-American War

April 1898 – August 1898, Spanish American War.

June 2, 1899 – July 4, 1902, Philippine–American War.

After its independence in 1821 and brief experiment with monarchy, Mexico became a republic in 1824, characterized by considerable instability, so that when war broke out in 1846, Mexico was ill-prepared for this conflict. The war with the US followed in the wake of decades of Indian raids in the sparsely settled north of Mexico, which the avenger government-sponsored Anglo-American migration to the Mexican province of Texas was aimed at buffering. Anglo-Americans and some Mexicans revolted against the Mexican government in the 1836 Texas Revolution, creating a republic not recognized by Mexico, which still claimed it as its national territory. The 1845 expansion of US territory with its annexation of Texas escalated the dispute between the US and Mexico to open war.

More Info: en.wikipedia.org