Complex sentence: The army was called in but as it was away from the city on military maneuvers, it only arrived on October 24, under the command of Lt Colonel Roberto Silva Renard who immediately imposed martial law upon the city.
Split into simpler sentences: The army was called in, but it was away from the city, on military maneuvers. It only managed to arrived on October 24, under the command of Lt. Colonel Roberto Silva Renard, who immediately imposed martial law upon the city.