Question: What isJuan Valentín Amador through its connection to Antonio López de Santa Anna?

Context paragraphs:
Valentín Canalizo: José Valentín Raimundo Canalizo Bocadillo (12 February 1795 – 20 February 1850), known as General Valentín Canalizo, son of Vicente Canalizo and María Josefa Bocadillo and baptized on 16 February 1795 at the Metropolitan Cathedral of Monterrey, was a Mexican President, state governor, city mayor, army general, defense minister and conservative politician.  He is as yet the only Mexican President from the city of Monterrey.  He was a supporter of a centralist (as opposed to a federalist) national government, and a confidante of President of Mexico General Antonio López de Santa Anna.  Canalizo was President of Mexico two times, for a total of about one year in 1843 and 1844, during the complex Mexican historical times after the one decade-long Mexican War of Independence and before the Mexican-American War.  Valentín Canalizo had previously been the Mayor of Mexico City, after being Governor of Puebla state, and years before, Mayor of the city of Cuernavaca.

Plan of Ayutla: The Plan of Ayutla was the 1854 written plan aimed at removing conservative, centralist President Antonio López de Santa Anna from control of Mexico during the Second Federal Republic of Mexico period.  Initially, it seemed little different than other political plans of the era, but it is considered to be the first act of the Liberal Reform in Mexico.  It was the catalyst for revolts in many parts of Mexico, which led to the resignation of Santa Anna from the presidency, never to vie for office again.  The next Presidents of Mexico were the liberals, Juan Álvarez, Ignacio Comonfort, and Benito Juárez.  The new regime would then proclaim the 1857 Mexican Constitution, which implemented a variety of liberal reforms.

José de Urrea: José de Urrea (March 19, 1797 – August 1, 1849) was a Mexican general.  He fought under General Antonio López de Santa Anna during the Texas Revolution.  Urrea's forces were never defeated in battle during the Texas Revolution.  His most notable success was that of the Goliad Campaign, in which James Fannin's 400 soldiers were surrounded and induced to capitulate under terms, but were massacred in Urrea's absence on the orders of Santa Anna.  Urrea also fought in the Mexican-American War.

National Theatre of Mexico: The National Theatre of Mexico (Teatro Nacional de México )is a theatre in Mexico City that host events that showcase the artistic and musical talents of Mexico.  It was formerly known as the Santa Anna Theatre, named after President of Mexico Antonio López de Santa Anna.  While it was called its former name, the theatre was captured by the advancing American forces and sacked during the course of the Mexican-American War.  

Juan Álvarez: Juan Nepomuceno Álvarez Hurtado de Luna, generally known as Juan Álvarez, (27 January 1790 – 21 August 1867) was a general, long-time caudillo (regional leader) in southern Mexico, and interim president of Mexico for two months in 1855, following the liberals ouster of Antonio López de Santa Anna.  Álvarez had risen to power in the "tierra caliente" (hot country) of southern Mexico with the support of indigenous peasants whose lands he protected.  He fought with heroes of the insurgency, José María Morelos and Vicente Guerrero in the War of Independence, and went on to fight in all the major wars of his day, from the "Pastry War", to the Mexican-American War, and the War of the Reform to the war against the French Intervention.  A liberal reformer, a republican and a federalist, he was the leader of a revolution in support of the Plan de Ayutla in 1854, which led to the deposition of Santa Anna from power and the beginning of the political era in Mexico's history known as the Liberal Reform. " Álvarez was most important as a champion of the incorporation of Mexico's peasant masses into the polity of [Mexico] ...advocating universal male suffrage and municipal autonomy."

Gadsden Purchase: The Gadsden Purchase (known in Mexico as Spanish: "Venta de La Mesilla" , "Sale of La Mesilla") is a 29670 sqmi region of present-day southern Arizona and southwestern New Mexico that the United States purchased via a treaty signed on December 30, 1853, by James Gadsden, U.S. ambassador to Mexico at that time.  The U.S. Senate voted in favor of ratifying it with amendments on April 25, 1854, and then transmitted it to 14th President Franklin Pierce.  Mexico's government and its General Congress or Congress of the Union took final approval action on June 8, 1854.  The purchase was the last substantial territorial acquisition in the contiguous United States.  The U.S. sought a better route for the construction of the southern transcontinental railway line.  The financially-strapped government of Antonio López de Santa Anna agreed to the sale, which netted Mexico $10 million dollars.  After the devastating loss of Mexican territory to the U.S. in the Mexican-American War (1846–48) and the continued filibustering by U.S. citizens, Santa Anna may have calculated it was better to yield territory by treaty and receive payment rather than have the territory simply seized by the U.S.

Battle of the Alamo: The Battle of the Alamo (February 23 – March 6, 1836) was a pivotal event in the Texas Revolution.  Following a 13-day siege, Mexican troops under President General Antonio López de Santa Anna launched an assault on the Alamo Mission near San Antonio de Béxar (modern-day San Antonio, Texas, United States), killing all of the Texian defenders.  Santa Anna's cruelty during the battle inspired many Texians—both Texas settlers and adventurers from the United States—to join the Texian Army.  Buoyed by a desire for revenge, the Texians defeated the Mexican Army at the Battle of San Jacinto, on April 21, 1836, ending the revolution.

Antonio López de Santa Anna: Antonio de Padua María Severino López de Santa Anna y Pérez de Lebrón (] ; 21 February 1794 – 21 June 1876), often known as Santa Anna or López de Santa Anna was a Mexican criollo who fought to defend royalist New Spain and then for Mexican independence.  He served as a Mexican politician and general.  He greatly influenced early Mexican politics and government, and was a skilled soldier and cunning politician, who dominated Mexican history in the first half of the nineteenth century to such an extent that historians often refer to it as the "Age of Santa Anna".  He was called "the Man of Destiny", who "loomed over his time like a melodramatic colossus, the uncrowned monarch."  Santa Anna first opposed the movement for Mexican independence from Spain, but then fought in support of it.  Though not the first "caudillo" (military leader) of modern Mexico, he "represents the stereotypical caudillo in Mexican history," and among the earliest.  Conservative historian, intellectual, and politician Lucas Alamán wrote that "The history of Mexico since 1822 might accurately be called the history of Santa Anna's revolutions... His name plays the major role in all the political events of the country and its destiny has become intertwined with his."

Juan Valentín Amador: Juan Valentín Amador (1793 – 1848) was a general in the Mexican army of the 19th century.  He served under Mexican President Antonio López de Santa Anna during the Texas revolution.

Treaties of Velasco: The Treaties of Velasco were two documents signed at Velasco, Texas (now Surfside Beach, Texas) on May 14, 1836, between Antonio López de Santa Anna of Mexico and the Republic of Texas, in the aftermath of the Battle of San Jacinto on April 21, 1836.  The signatories were Interim President David G. Burnet for Texas and Santa Anna for Mexico.  The treaties were intended, on the part of Texas, to provide a conclusion of hostilities between the two belligerents and to offer the first steps toward the official recognition of the breakaway republic's independence.

Supporting paragraphs: Juan Valentín Amador Antonio López de Santa Anna
Answer: served under Mexican President