Until the reforms of Gaius Marius, Rome had no standing professional army, the army always has been the core of the Roman society. No political carreer was possible without having served in the army
King
Servius Tulius,
according to Titus Livius, reorganized the Roman army and created the
taxing
system (census) on which the position and armament of each man was
determened.
Polybius 6.12:
As soon as the consuls are declared, the military
tribunes are next appointed. Of these, fourteen are taken from the citizens who
have carried arms in five campaigns; and ten more from those who
completed ten. For every citizen, before he arrives at the age of
forty-six, is obliged to serve either ten years in the cavalry, or
sixteen in the infantry: those alone excepted who are placed by the
censors below the rate of four hundred drachmae; and who are all
reserved for the service of the sea. In the case of any pressing danger
the time of continuing in the infantry is extended to twenty years. No citizen is permitted by the
laws to sue for any magistracy before he has completed the serving of
ten campaigns.
When the enrollments are
to be made the consuls give notice before to the people of a certain
day, upon which all the Romans that are of sufficient age are required
to attend. This is done every year. And when the day arrives, and the
men all appear at Rome, and are assembled afterwards in the Capitol,
the tribunes of the youngest order divide themselves, as they are
appointed either by the consuls or the people, into four separate
bodies. For this division corresponds with the first and general
distribution of all the forces into four separate legions. Of these
tribunes, therefore, the four first named are assigned to the first
legion; the three next to the second; the
following four to the
third; and the last three appointed to the fourth. Of the tribunes of
the oldest order the two that are first named are placed in the first
legion; the three second in the second; the two that follow in the
third; and the remaining three in the fourth. By this distribution and
division an equal number of commanders is allotted to each legion.
When this is done, the
tribunes of each legion, having taken their seats apart, draw out the
tribes one by one by lot; and calling to them that upon which the lot
first falls, they select from it four young men, as nearly equal as is
possible in age and stature. And when these are brought forward from
the rest, the tribunes of the first legion first choose one; then those
of the second a second; those of the third take the third; and those of
the fourth the last. After these four more are made to approach. And
now the tribunes of the second legion first make their choice; then
those of the rest in order; and last of all the tribunes of the first.
In the same manner again, from the next four that follow, the tribunes
of the third legion choose the first; and those of the second the last.
And thus, by observing the same method of rotation to the end, it
happens that the legions, with respect to the men of which they are
composed are all alike and equal. The number allotted to each legion is
four thousand and two hundred; and sometimes five thousand, when any
great and unusual danger is foreseen. After these had been thus
selected it was anciently the custom to choose the cavalry; and to add
two hundred horsemen to each four thousand of the infantry But in the
present times, the citizens, of whom the cavalry is composed, are first
enrolled; having been before appointed by the censors, according to the
rate of their revenue; and three hundred are assigned to every legion.
Of course the armament of this army and the way it would operate was considerably different from the imperial period. Since there are 700 years in between, this is to be expected. The Romans didn't mind copying idees from other peoples. As long as it would improve the Roman army, they would adapt.
The base of the Roman army was of course the legionaire.
More than anything else the army depended on the infantry. The cavalry was mainly
there to protect the flanks in battle and reconnaissance For rich young men, wanting a political
career, the cavalry was the opportunity to make themselves noticed.
These legionaires together formed the legion.
From the time Rome had forced the conquered cities to be allies of Rome, they had also to produce soldiers. Most of the cavalry was delivered by the allies.
In the republican era a consular army existed of two Roman legions in the centre and at each wing an ala with allied soldiers commanded by a Roman. An Ala was organised in a simalar way as the Roman legion.