On March 27, 1846, troops under the command of General Zachary Taylor advanced to a north bank of the Rio Grande and began construction of an earthen star fortress that they named Fort Taylor but was nicknamed "Fort Texas". Mexican forces ambushed a troop of United States Cavalry, and then lay siege to the unfinished Fort Texas. The American garrison consisted of Major Brown's 7th Infantry, Captain Loud's artillery company of four 18 pounders, and Lieutenant Bragg's light artillery company of four more guns.