Quote Originally Posted by Pannonian View Post
Polybius has a full description of the selection process. IIRC the Roman territories have an obligation to provide n men for service. The selection will take into account fitness for service, service already rendered, the consul's choice, etc. They then make their way to a gathering point, eventually meeting up on the Field of Mars. When Hannibal marched on Rome in an attempt to relieve Capua, 4 legions had coincidentally just been raised and assembled in Rome.

Also, training might still have been done by parents and parent figures at this point in time. It was Scipio Africanus, during his Iberian campaign, who brought in gladiator-style standardized training.
So, the Roman armies of the period were likely made up of a mixture of full time professionals, recalled veterans (reservists of a kind), and a large number of hastily, but well trained recruits. Their pattern of tactics must have therefore, become predictable to an astute General. Hannibal was certainly an astute tactician. He seemed to have an uncanny knack of getting well inside the decision making process of his Roman opponents.