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. (3) See "Revenues," iv. 30. (4) Decadarchs, lit. commanders of ten, a "file" consisting normally (or ideally) of ten men. Cf. "Cyrop. II." ii. 30; VIII. i. 14. It will be borne in mind that a body of cavalry would, as a rule, be drawn up in battle line at least four deep (see "Hell." III. iv. 13), and frequently much deeper. (The Persian cavalry in the engagement just referred to were twelve deep.) (5) See "Cyrop." III. iii. 41, 57; VI. iii. 24, 27; VII. i. 15; "Pol. Lac." xi. 5. These front-rank men would seem to correspond to our "troop guides," and the rear-rank men to our serre-files to some extent. (6) Cf. Aelian Tact. 26, ap. Courier. The interval between the front and rear-rank men will best be filled supposing that the decadarchs are free to choose their own supports, and those chosen theirs, and so on following suit; since on this principle we may expect each man to have his trustiest comrade at his back. As to your lieutenant, (7) it is every way important to appoint a good man to this post, whose bravery will tell; and in case of need at any time to charge the enemy, the cheering accents of his voice will infuse strength into those in front; or when the critical moment of retreat arrives, his sage conduct in retiring will go far, we may well conclude, towards saving his division. (8) (7) {ton aphegoumenon}, lit. "him who leads back" (a function which would devolve upon the {ouragos} under many circumstances). Cf. "Cyrop." II. iii. 21; "Hell." IV. viii. 37; Plat. "Laws," 760 D. = our "officer serre-file," to some extent. So Courier: "Celui qui commande en serre-file. C'est chez nous le capitaine en second." (8) Or, "the rest of the squadron." Lit. "his own tribesmen." An even number of file-leaders will admit of a greater number of equal subdivisions than an odd.