page_title: Mexican–American War
section_title: Challenges in the United States
hierarchical_section_title: Mexican–American War / Preparation for war / Challenges in the United States
caption_attribution_description: English: Full dress and campaign uniforms, 1835-1851.
context_page_description: The Mexican–American War, also known in the United States as the Mexican War and in Mexico as the Intervención Estadounidense en México, was an armed conflict between the United States and Mexico from 1846 to 1848. It followed the 1845 U.S. annexation of Texas, which Mexico still considered Mexican territory since the government did not recognize the treaty signed by Mexican General Antonio López de Santa Anna when he was a prisoner of the Texian Army during the 1836 Texas Revolution. The Republic of Texas was defacto an independent country, but most of its citizens wished to be annexed by the United States. Domestic sectional politics in the U.S. prevented that since Texas would have been a slave state, upsetting the balance of power between northern free states and southern slave states. In the 1844 United States presidential election, Democrat James K. Polk was elected on a platform of expanding U.S. territory in Oregon and Texas. Polk advocated expansion by either peaceful means or by armed force, with the 1845 annexation of Texas as furthering that goal. For Mexico, this was itself a provocation, but Polk went further, sending U.S.
caption: U.S. Army full dress and campaign uniforms, 1835-1851.
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