From Maniple to
The basic unit of the Roman
army was the legion, essentially a division of 4,500-5,000 men. The
smallest unit of the legion was a century -- comprised of about 60-80 men. Each
legion contained 60 centuries headed by a centurion. Roman tradition
dictated that the centurions be promoted from the ranks based on their courage,
experience, initiative and skill. Centurions were responsible for the
training and conduct of the men beneath them. They combined the functions and
prestige of a modern company commander and senior sergeant.
In the early days of the Republic, the centuries were paired into groups
called maniples. The legion's thirty maniples were then arranged, widely
spaced, into three lines of ten maniples each. In the first line, called
the hastati, the men stood three deep and forty across. The second
line (principes) stood twelve wide by ten deep. The maniples of the
third line were smaller than the first two and stood six wide and ten
deep. In battle formation the hastati extended across the line of
battle. The principes and triari stood to the rear but not
directly behind the hastati, instead they were offset diagonally creating
a checkerboard effect.
The manipular formation was small enough to allow the army some articulation
(the word maniple comes from the Latin for "hand," while phalanx derives from
the Greek word for "finger") and some flexibility of movement. Tactically,
the units were small enough to maneuver on the battlefield with minimal training
and were effective at flanking movements which the typical phalanx of the
Alexandrian system could not match. Each maniple possessed its own set of
standards, originally a handful of hay set on a pole, whose movements served for
the transmission of orders.
The manipular legion served the Romans well for over two hundred years, but
it suffered from tactical and organizational problems. The same dispersion
that allowed a maniple the flexibility to flank opponents, proved to be
vulnerable to direct onslaughts. The small size of the maniple proved to be too
"light" and a clever enemy could isolate and overwhelm a single maniple.
The other problem was that none of the legion's subdivision lent themselves to
detachment for special duties.
Marius reorganized the legion by abolishing the maniple as a tactical unit,
thus eliminating the last vestiges of the old phalangeal organization. In
its place he introduced a completely rational plan of articulation. He
re-grouped the legion's centuries into ten cohorts of 500-600 men each.
This served to reconcentrate the legion's strength into larger units. Each
cohort contained six centurions of different grades who provided the necessary
continuity in the chain of command.
With the elimination of the maniples, Marius also eradicated the traditional
three lines. With cohorts as the basic operational unit, the legion’s men
could be deployed into as few or as many lines as the circumstances warranted.
The reform also reduced vulnerability to cavalry because its excellent
articulation allowed parts of the army, legion or cohort, to maneuver to protect
a flank, and the good subdivision permitted the commander to assign a unit or
units to flank protection. Since formed heavy infantry could stop the charge of
formed heavy cavalry, Roman commanders felt little anxiety about their flanks
with this setup.
At the same time, Marius (and those who followed) clarified the command
structure. From the overall commander of the army through the legates,
military tribunes, centurions and common soldier, every commander had full
authority over the men in the unit he commanded. He, in turn, was
answerable to a commander over him. The Roman practice of subdivision and
subordination had another advantage -- it gave real scope for the initiative of
subordinates on the battlefield. Battlefield communications were so poor
once battle was joined that the role of the general was primarily one of
determining when to commit the reserve. For that reason Roman commanders
harangued their troops before combat. The speech was not only for morale
boosting but to give the men a general outline of the overall plan so that they
could execute it without a steady stream of orders. More than once a legion had
been saved when centurions or tribunes did what they were expected to do without
a general in earshot. Furthermore, while normally considered to be a
tactical alteration, the cohort system also gave a commander units with enough
strength to defend themselves and that could easily be separated from the rest
of the legion to carry out special duties. Marius thus created a fully
articulated army capable of maneuvering and responding promptly to the orders of
On the battlefield, cohorts assumed a formation about five hundred feet wide
by fifty feet deep. In another departure from the manipular formation, the
cohort formed a continuous front while engaged in hand to hand fighting. In
action, the lines of the cohort rotated, allowing a fresh line to appear at
regular intervals of about 10 minutes. The engaged line withdrew and fell to
rear until its turn came again. No other opponent operated in this fashion,
hence an attacking force was continuously faced with relatively fresh troops
during the entire battle. Eventually the enemy could no longer stand the strain
and would succumb to exhaustion. If they broke, the hasty disorganized
retreat usually turned into a fatal rout.
The first real test of the Marian tactical system came at Aix-En- Provence
when a combined army of Ambrones and Teutones, numbering around 130,000 warriors
confronted Marius consular army of six legions. The battle was one-sided and
resulted in the extermination of both tribes -- Marius took 17,000 warriors
prisoner and another 130,000 dependents. The following year, at Vercellae
in the Po valley, Marius defeated the Cimbri, killing 140,000 and enslaving
60,000 warriors, and taking a like number of women and children prisoners.
The German threat was removed. Marius was elected consul for the 6th time,
and hailed the "Third Founder of Rome." The Marian tactical system became
the model for the rest of Rome's history.