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The crisis in Spain (including the deposition of the Spanish king) undermines Spanish authority over its colonies, setting the stage for independence movements in New Spain.
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On September 16, Father Miguel Hidalgo y Costilla issues the call to arms in Dolores, Guanajuato, marking the beginning of the Mexican War of Independence.
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Spanish royalist forces defeat insurgent armies, forcing the revolutionary movement to regroup and adapt its strategies.
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Insurgent leaders promulgate this constitution as a framework for self-governance and the establishment of an independent state.
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After early setbacks, Vicente Guerrero emerges as a key leader, sustaining the fight for independence in southern Mexico.
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Political changes in Spain (including the reinstatement of the Cadiz Constitution) influence reforms in New Spain and open a path toward negotiations with insurgent forces.
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Agustín de Iturbide proclaims a plan based on three guarantees—independence, equality, and protection of the Catholic faith—that unites royalists and insurgents.
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Signed on August 24, this treaty confirms Mexican independence from Spain.
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The Army of the Three Guarantees enters Mexico City on September 27, symbolically ending Spanish colonial rule.
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Agustín de Iturbide is declared Emperor of Mexico, marking the nation's first attempt at an independent monarchical system.
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Facing internal opposition and instability, Iturbide abdicates in March, paving the way for a republican form of government.
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Promulgated on October 4, this constitution establishes Mexico as a federal republic.
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Political struggles between federalist and centralist factions intensify as Mexico works to consolidate its new state.
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Discontent grows among settlers in the Mexican province of Texas, eventually leading to an armed rebellion against central authority.
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Texas declares its independence from Mexico following pivotal conflicts such as the siege of the Alamo and the victory at San Jacinto (April 21).
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The Republic of Texas is annexed by the U.S., a move that heightens tensions between Mexico and the United States.
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Start of the Mexican–American War – Disputes over the Texas border and American expansionism lead to war on April 25.
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Signed on February 2, this treaty ends the Mexican–American War. As a result, Mexico cedes vast territories—including what are now Texas and California—to the United States.