By the end of 1835, no Mexican troops remained in Texas. As early as October, however, Mexican President Antonio Lopez de Santa Anna had been making plans to quell the unrest in Texas. He stepped down from his duties as president to lead what he dubbed the Army of Operations in Texas, which would put an end to the Texas revolt. Personally leading his forces, Santa Anna crossed the Rio Grande on February 12. Santa Anna and his advance force arrived in San Antonio de Bexar on February 23 and immediately initiated a siege of the Texas forces garrisoned at the Alamo.