slaves. Legions could contain as many as 11,000 fighting men when including the auxiliaries. During the Later Roman Empire, the legion was reduced in size to 1,000 to allow for easier provisioning and to expand the regions under surveillance. Numbers would also vary depending on casualties suffered during a campaign; Julius Caesar's legions during his campaign in Gaul often only had around 3,500 men. Tactics were not very different from the past, but their effectiveness was largely improved because of the professional training of the soldiers. After the Marian reforms and throughout the history of Rome's Late Republic, the legions played an important political role. By the 1st century BC, the threat of the legions under a demagogue was recognised. Roman governors were not allowed to leave their provinces with their legions. When Julius Caesar broke this rule, leaving his province of Gaul and crossing the Rubicon into Italy, he precipitated a constitutional crisis. This crisis and the civil wars which followed brought an end to the Republic and led to the foundation of the Empire under Augustus in 27 BC. Early Empire (27 BC–AD 284) See List of Roman legions of the early Empire See also Sub-Units of the Roman legion Generals, during the recent Republican civil wars, had formed their own legions and numbered them as they wished. During this time, there was a high incidence of Gemina (twin) legions, where two legions were consolidated into a single organisation (and was later made official and put under a legatus and six duces). At the end of the civil war against Mark Antony, Augustus was left with around fifty legions, with several double counts (multiple Legio Xs for instance). For political and economic reasons, Augustus reduced the number of legions to 28 (which diminished to 25 after the Battle of Teutoburg Forest, in which three legions were completely destroyed by the Germanics). Beside streamlining the army, Augustus also regulated the soldiers' pay. At the same time, he greatly increased the number of auxiliaries to the point where they were equal in number to the legionaries. He also created the Praetorian Guard along with a permanent Roman Navy where served the liberti, or freed slaves. The legions also became permanent at this time, and not recruited for particular campaigns. They were also allocated to static bases with permanent castra legionaria (legionary fortresses). Augustus' military policies proved sound and cost effective,