Q: In this task, you're given passages that contain mentions of names of people, places, or things. Some of these mentions refer to the same person, place, or thing. Your job is to write questions that evaluate one's understanding of such references. Good questions are expected to link pronouns (she, her, him, his, their, etc.) or other mentions to people, places, or things to which they may refer. Do not ask questions that can be answered correctly without understanding the paragraph or having multiple answers. Avoid questions that do not link phrases referring to the same entity. For each of your questions, the answer should be one or more phrases in the paragraph, and it should be unambiguous.
Passage: Santa Anna had successfully escaped towards Vince's Bridge.  Finding the bridge destroyed, he hid in the marsh and was captured the following day. He was brought before Houston, who had been shot in the ankle and badly wounded. Texian soldiers gathered around, calling for the Mexican general's immediate execution.  Bargaining for his life, Santa Anna suggested that he order the remaining Mexican troops to stay away.  In a letter to Filisola, who was now the senior Mexican official in Texas, Santa Anna wrote that "yesterday evening [we] had an unfortunate encounter" and ordered his troops to retreat to Béxar and await further instructions.Urrea urged Filisola to continue the campaign.  He was confident that he could successfully challenge the Texian troops.  According to Hardin, "Santa Anna had presented Mexico with one military disaster; Filisola did not wish to risk another."  Spring rains ruined the ammunition and rendered the roads almost impassable, with troops sinking to their knees in mud.  Mexican troops were soon out of food, and began to fall ill from dysentery and other diseases.  Their supply lines had completely broken down, leaving no hope of further reinforcements. Filisola later wrote that "Had the enemy met us under these cruel circumstances, on the only road that was left, no alternative remained but to die or surrender at discretion".For several weeks after San Jacinto, Santa Anna continued to negotiate with Houston, Rusk, and then Burnet.  Santa Anna suggested two treaties, a public version of promises made between the two countries, and a private version that included Santa Anna's personal agreements.  The Treaties of Velasco required that all Mexican troops retreat south of the Rio Grande and that all private property—code for slaves—be respected and restored.  Prisoners-of-war would be released unharmed, and Santa Anna would be given passage to Veracruz immediately.  He secretly promised to persuade the Mexican Congress to acknowledge the Republic of Texas and to recognize the Rio Grande as the border between the two countries.When Urrea began marching south in mid-May, many families from San Patricio who had supported the Mexican army went with him.  When Texian troops arrived in early June, they found only 20 families remaining.  The area around San Patricio and Refugio suffered a "noticeable depopulation" in the Republic of Texas years.  Although the treaty had specified that Urrea and Filisola would return any slaves their armies had sheltered, Urrea refused to comply. Many former slaves followed the army to Mexico, where they could be free.  By late May the Mexican troops had crossed the Nueces.  Filisola fully expected that the defeat was temporary and that a second campaign would be launched to retake Texas.
A:
What is the name of the person who secretly promised to persuade the Mexican Congress to acknowledge the Republic of Texas and to recognize the Rio Grande as the border between the two countries?