The actual plan of defense, as of February 1836, is another topic of historical debate. Until recently, the map generally cited by historians has been the plan drawn by Green Jameson in January 1836. The original of this map has disappeared, but the plan survives in several publications, apparently in very modified form (Figure 2). Two other maps, drawn in 1836 but relatively ignored, are those of Colonel Sanchez-Navarro (Figure 3), who returned with Santa Anna in February 1836 after retreating with Cós after the surrender of San Antonio in December 1835; and of Colonel Ygnacio de Labastida (Figure 4), the commander of engineers of the army of the north under Santa Anna. These maps agree well with the descriptions left by eyewitnesses de la Peña (1975[1836]) and Filisola (1965[1836]). Sanchéz-Navarro includes a detailed index and discussion with his map. The maps agree, in general, on the location of the various buildings within the Alamo and the placement of the guns. Sanchez-Navarro's map, apparently drawn from memory and notes in mid-1836 after his second retreat from Texas, is the least trustworthy in terms of agreement of the details of his plans and discussion with known facts and with the other maps and narratives.
The 1836 maps show that no traces of the convento building east of those facing onto the Main Plaza of the mission had survived the long neglect from about 1812 until the fortification in 1835. In fact, much of the ruins of these structures was probably used in construction of the gun platform in the Alamo church since, as stated earlier and contrary to tradition, the church was not full of the ruins of its vaults and towers, but only a little rubble from the ribs of the nave and the vault over the apse. In the north courtyard, these maps show a gun platform and ramp at the northeast corner of the walls and a trench along the interior of the walls. The map drawn by Sanchéz-Navarro shows ditches along the north and east walls of the courtyard, while Labastida's map depicts a ditch along only the north wall. Both maps show the edge of the trench facing inward toward the courtyard as denticulate, the width of the ditch varying in rectangular zigzags. Labastida's map further indicates a circular ditch outside the northeast corner of this courtyard, protecting the gun platform.
When the Alamo fell on March 6, 1836, the Mexican army reorganized and marched eastward, pursuing General Houston and the Texan forces. A garrison was left in San Antonio under the command of General Juan Andrade. Among other duties, Andrade was ordered to repair and improve the defenses of the