Mexico was a nation in North America that today refers to several territories in the same region. The homeland of some of America's greatest civilizations, including the Olmec,Mayan, and Aztec, Mexico was conquered by the Spanish in the 16th century. Gaining independance in 1821, Mexico remained a poor nation that was dominated by foreign powers. When Portfirio Diaz was overthrown, a civil war broke out leading to the ascension of Emilio Zapata, who was largely able to unite the warring factions when Mexico entered World War I on the side of the Central Powers. The United States, in response to an attempted Mexican invasion, launched its' own invasion of Mexico, which resulted in annexation in 1918. Rebellions continued, especially in the 1930's, under the banner of the Latin American Unio