The Army and Its Divisions.
The Legions.The Roman legion corresponded to a modern Division, but was more an organic whole, since it was the smallest unit that had separate line officers. What its normal strength was in Caesar's time we have no means of knowing; but a probable estimate puts it at 5000 men. The actual effective strength in the field, however, was usually much less, falling to 3000 men, as at the battle of Pharsalia (on Caesar's own authority). This variation in number was due to the many absences from duty which always occur in a military organization, and to the losses incurred by the individual legions in previous campaigns. Losses in old legions were not usually made good by new recruits, but the latter were formed into new legions; hence the older the legion, the smaller usually its enrollment. The average effective strength of the legion in the Gallic War was probably near 3600 men. The subdivisions of the legions were as follows:
|1 legion||10 cohorts of about 360 men each.|
|1 cohort||3 maniples of 120 men each.|
|1 maniple||2 centuries of 60 men each.|