Praetorian (Civ4)/Civilopedia

The Roman Legions, created during the early wars of the Republic and tested during the three Punic Wars against Carthage, were the fighting force that conquered and held the Roman Empire together for five centuries. Each legion was composed of 6000 men, divided into 60 smaller groups known as centuries. Nearly unstoppable on the attack, the legion was relatively weak on defense. The legion's demise as a military unit was accelerated by the destruction of Emperor Valens' army by Gothic knights in the fourth century.
The term "Praetorian" came from the tent of the legatus of a legion in the field-the praetorium. It was a habit of many Roman generals to choose a private force of soldiers from the ranks to act as bodyguards of the tent or the person. These elite troops consisted of both infantry and cavalry. In time, this cohort came to be known as the cohors praetoria; various notable figures possessed one, including Julius Caesar, Mark Antony and Augustus Caesar (Octavianus). As Julius Caesar discovered with the Legio X Equestris, a powerful unit more dangerous than its fellow legions was desirable in the field. When Augustus became the first ruler of the Roman Empire in 27 BC, he decided such a formation was useful not only in war but in politics. Thus, from the ranks of the legions throughout the provinces, Augustus recruited the Praetorian Guard.