Given, then, that your troopers are thoroughly trained in all the
above particulars, it is necessary, I presume, that they should
further be instructed in a type of evolution the effect of which will
show itself not only in the splendour of the great processions[1] in
honour of the gods, but in the manouvres of the exercising-ground; in
the valorous onslaught of real battle when occasion calls; and in the
ease with which whole regiments will prosecute their march, or cross a
river, or thread a defile without the slightest symptom of confusion.
What this formation is--essential, at least in my opinion, to the
noblest execution of their several duties--I will now, without delay,
endeavour to explain.[2]

[1] e.g. the Panathenaic, as depicted on the frieze of the Parthenon.

[2] Or, "what this best order is, the adoption of which will give
these several features fair accomplishment, I will without further
pause set forth."

We take as our basis, then, the constitutional division of ten
tribes.[3] Given these, the proper course, I say, is to appoint, with
the concurrence of the several phylarchs, certain decadarchs
(file-leaders)[4] to be selected from the men ripest of age and
strength, most eager to achieve some deed of honour and to be known to
fame. These are to form your front-rank men;[5] and after these, a
corresponding number should be chosen from the oldest and the most
sagacious members of the squadron, to form the rear-rank of the files
or decads; since, to use an illustration, iron best severs iron when
the forefront of the blade[6] is strong and tempered, and the momentum
at the back is sufficient.