Sage, Michael M. (2008), The Republican Roman Army: A Sourcebook, London & New York: Routledge, ISBN0-415-17879-7.
Page 2: An interesting note here that the major historians from antiquity often ignored the technical aspects of warfare and institutional development, whereas ancient Roman antiquarian writers focused specifically on technical aspects. The exception is the 2nd-century BC Greek historian Polybius, who had military experience and was fascinated with the Roman maniple unit, specifically how it won for Rome an empire and could be compared with the Greek phalanx formation.
The development of the cohort as a tactical unit[edit]
Page 199: In the early 1st century BC, the maniple (military unit) was replaced by the cohort (military unit). It is unclear in which exact year this took place, or even where the term cohort comes from, although it was previously used when referring to allied infantry units. They comprised 600 men at most, led by a praefectus cohortis. The earliest evidence for the cohort in Roman armies comes from the Second Punic War, including the Battle of Ilipa against Carthage in what is now Spain. QUOTE: "Polybius defines [the cohort] as a unit of three maniples with their accompanying light-armed [sic]. Polybius' statement implies that the cohort was by his time a regular military unit."
Page 199-200: Livy also mentions the cohort and maniple as used by Scipio Africanus in the Iberian Peninsula, althouogh Livy may have misunderstood what a true maniple was, and could have anachronistically applied the phrase "cohort" in situations when it should have been a maniple.
Page 200: The last known reference (made by the historian Sallust) to a maniple used in battle belongs to the campaign of Quintus Caecilius Metellus Numidicus against Numidia in the Jugurthine War, although it is written that cohorts were also employed. It seems that the early cohorts were viewed as being useful for independent operations and rapid movement, but they gradually became the primary infantry unit to replace the smaller maniple.
Page 200: QUOTE "The use of the cohort structure would have simplified the exercise of command. Orders could now have to be transmitted to ten rather than thirty units. It has also been suggested that these larger units would have dealt more effectively with the irregular formations of barbarian troops. However, during Rome's encounters in Italy with Celtic forces that fought in just such a dispersed fashion, the maniple seems to have been effective. It was rather the dispersed operations that the Romans encountered in Spain and elsewhere in the West that increased reliance on the cohort as a basic tactical element. Once homogeneity of equipment developed there was little point in reforming units into maniples and discarding the advantages of a simplified command structure. The change was once seen as a military innovation of Marius to be connected with his struggle with Germanic invaders in the last years of the second century. It is more likely that the change was the product of a long and continuous process."
Page 201: "Some have taken the combined use of the cohort and maniple as marking a transitional phrase, and they may be right. However, the terminology is unclear. The reference could be either to a tactical formation or simply to a section of a legion. Sallust's account of this war contains the last references to the use of the maniple in battle; for this reason many scholars accept that Marius introduced the cohort as a tactical unit in battle. It seems more likely that this period saw the end of a long evolution from maniple to cohort and that Marius simply extended a practice already evident in the account of Metellus' tactics."
Page 238: QUOTE: "Elected consul in 107, despite aristocratic opposition, with a combination of plebeian and equestrian support, Marius received the command of the war against Jugurtha which the Romans had been waging since 111 with indifferent success. The Senate allowed him to levy a supplement to the existing consular army of two legions already in Africa. Such supplements are attested as early as the Second Punic War and were frequently used in Spain."
Page 238: QUOTE: "Marius' use of volunteers also had earlier precedents, such as Scipio Aemilianus (see 156) for the campaign in Spain in 134. The innovation he introduced was to allow men to serve in the legions who fell below the minimum property rating. Such men had served before but only in emergencies (see p. 197). This change seems to have become standard practice from this point on. Marius' actions marked the end of a long evolution marked by the continued fall in the property rating necessary to qualify for legionary service. At the point that Marius held his levy there would have been little difference in wealth between the poorest of those liable to serve and those even worse off. The importance of the step was that it now opened up the possibility of new employment for those who had few other prospects. It also, at least in part, created the possibility for the development of a semi-professional army, given the meager prospects for the employment for many of the poor. The long-term service that Rome's expanding empire required could now be provided by such an army."
Page 238: QUOTE: "Nevertheless, the older form of levy according to census classes continued, though our evidence for them is not very full."
Page 239: QUOTE: "In considering the effects of long-term service it is important to keep in mind that such volunteers might often be in a position to influence the conduct of the rest of the troops. Generals such as Caesar were conscious of the value of experienced troops. It appears from Sallust's account that in Marius' levy many of the conscripts were plebeians from the city of Rome, though normally volunteers and conscripts both came from the same rural background. Given the pressure on the rural poor, this is hardly surprising, though the level of pay and its irregularity during the last century of the Republic would not by themselves have been strong attractions. But the prospect of booty, as the following passage makes clear, as well as donatives or money gifts to the troops, and the regularity of employment would have been attractive. Evidence for the changes in the orientation of the army is provided by the regularity of demands for land for demobilized veterans. Distributions of land had been made since the early Republic, but the intensity of demand after Marius' reform points to a change in the economic position of many of the troops."
Page 239: QUOTE: "Roman writers saw Marius' action as marking a break with earlier practice, though they may have exaggerated its immediate effects. They were correct in perceiving that, by enrolling those whose present and future economic security depended on their military service, Marius had begun a process of slowly widening the gap between the state and its armed forces."
