The Fall of Carthage by Adrian Goldsworthy

gaps between them. Far more importantly the intervals in the Roman line were covered by the maniples of the next line. 39
    All armies apart from the Romans tended to concentrate the vast majority of their infantry strength in a single line. Hellenistic armies, for instance, preferred to deepen their phalanx rather than form troops into a second line and made little or no use of reserves. This was in part because their commanders, usually monarchs, were obliged by tradition to fight in person at the head of their Guards and were in no position to send orders to reserve formations. The deepening of the phalanx also gave it great stamina in combat. In every battle over half of the Roman infantry were initially kept uncommitted in the second and third lines. Deeper lines had more stamina, but even the men in the rear ranks were affected by the exhaustion of prolonged combat. The Roman system allowed fresh men to be fed into the fighting line, renewing its impetus and leading a surge forward which might well have been enough to break the wearying enemy. The wide intervals between maniples made it easier to reinforce a combat in this way. Committing the reserve lines required careful judgement on the part of a Roman commander. Too early and the fresh troops risked being absorbed by the front line and sharing their exhaustion. Too late and the fighting line might collapse, perhaps even sweeping the second and third lines away in its rout. A good commander kept a tight rein of his reserve lines and restrained them from joining the combat on their own initiative, as excitable and nervous men and centurions were eager to join the fight. The triarii traditionally squatted or kneeled down in the third line. The posture made it easier for them to brace their spear-butts on the ground and present a hedge of point to the front, but it may also have been intended to discourage them from moving forward prematurely. The triarii numbered fewer than half of either of the first lines and traditionally offered a refuge for these to retire behind, hence the expression 'the affair came down to the triari? which applied to any desperate situation. 40
    The Roman military system was directed to the single end of applying massive, steadily renewed pressure to an enemy in front. The second and third lines were not true reserves in the modern sense, and only in the most experienced legions were they capable of any form of manoeuvre. The legion's drill and tactics were ideally suited to the formal, almost ritualized battles of the period. The marching camp with its formal layout and the wide lanes between the tent lines and behind the rampart allowed the troops to form up in the columns used to deploy into battle order and then each march out through one of the gateways. The large number of officers with the army helped to regulate and control this process. Indeed the system placed considerable responsibility in the hands of the general and senior officers, which in itself belies the old view that these men were inexperienced and scarcely necessary for the army to function. With much of the army kept in reserve at the beginning of an action, it was important that someone, usually the commander himself, took the decision to commit these fresh troops. Roman commanders did not charge spear in hand at the head of their Guard cavalry like Alexander the Great or the Successor Kings. On some occasions, especially in a desperate situation, a Roman general might choose to lead a charge, but he did not expect to spend the entire battle this way. Roman generals tended to stay near to the fighting without actually joining it, riding around just behind the fighting line. From this position they were able to encourage their men and also, through the noise made by and appearance of the men in combat, judge how well the action was going and issue orders to commit their reserves accordingly. The general needed to guess where the most important fighting would occur and move