On February 23, 1836, Mexican troops under General Antonio Lopez de Santa Anna took control of San Antonio de Bexar. Just before Santa Anna's arrival, the Texians retreated to the relative safety of the San Antonio de Valero Catholic Mission and the siege of the Alamo began. For twelve days, Santa Anna fired a continual cannon bombardment and attacked with a flurry of cavalry and infantry charges, all designed to keep the Alamo defenders stressfully awake. Late on March 5, the bombardment stopped, and the fatigued Alamo defenders fell into a deep sleep. The siege ended in the early hours of March 6 when Santa Anna committed over 2400 infantry and cavalry to attack the walls of the Alamo. By sunrise, all one 188 Alamo defenders had been brutally slaughtered to the last man.

This is how history recorded the battle, but is this how it really happened?

On February 23, 2010, an Army infantry squad, carrying ammunition to a training exercise is swept into a time rift. The rift takes them to the Alamo, thirteen days before it fell.