The AS332 "Superpuma" helicopter used for the film is the same bird that actually crashed in Afghanistan.
The helicopter that appears in the film is the real one, the Spanish army lent it for the realization.
The actors received military training by the Spanish army.
The AS332 "Superpuma" helicopter that crashed in Afghanistan actually belonged to the Spanish Airforce. In the film they make it seem that it belongs to the Spanish Army.
The words recited by the Spanish soldiers before the last attack are part of the "Décimo Espíritu del Credo Legionario" (The tenth spirit of the Spanish Legion Creed)