There is one general cause: that great [men] have always judged it to be of importance for wars to be waged successfully, and the most prudent, most warlike leaders and peoples have, by the thing itself, found by experience, that not just anyone should be taken up everywhere and rashly, but [that] a great and serious choice should be employed. And therefore Seneca, in the Epistles, says: “Camps [armies] receive fastidiously those whom they receive for labor and danger.” “The strength of the realm and of the Roman name,” says Vegetius (book 1, ch. 7), “consists in the first examination of the levies.” Nor — as Aristotle rightly warns in the Politics — [are] all [men] suited to all [things].
There are [those] for whom the Elean [Olympic] palm of the four-horse chariot runs; There are [those] for whom glory is born in swift feet.
And [so says] that most elegant Master of civil doctrine (book 5, ch. 8): “Of what use,” he says, “[is] a multitude of horse and foot, however great, if [it be] cowardly, unskilled, and only a multitude? Do thou know, from Seneca (6 On Benefits, ch. 31), [that] it has not strength but weight, and is — as Livy says (book 1) — a hindrance greater than a help.” A certain [one] of the Greeks aptly warned: χειρῶν δεῖ τῷ πολέμῳ καὶ οὐκ ὀνομάτων πολλῶν — that is, “In war there is need of hands, not of many names” (taking “names” here as I explained [on] Acts 1). For “in every conflict a multitude profits not so much as valor,” says the already-cited Vegetius (book 1, ch. 8); [and] also “in many legions [there are] few who decide the battles,” as Tacitus says (book 14 of the Annals). And therefore the best and bravest are each to be chosen. There are other, special causes: [namely] because Moses judged [it] not necessary to make trouble for the whole camp of the Israelites. For that [is] both troublesome and inglorious. And therefore, below (ch. 7, v. 3), those whom Joshua had sent to spy out Hai [Ai] say: “Let not all the people go up, but let two or three thousand men go and destroy the city. Why should all the people be troubled in vain against very few enemies?” But he appointed a few of the others, says Josephus, around the water gushing from the rock, to guard it; but very many around the guarding of the infants and the women. Then it is fore-signified…
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…[it is fore-signified] that the greatest roles [in this war] would belong to CHRIST JESUS himself — so that he might choose out for himself strenuous and robust men, whom he himself leads into the battle-line against all the forces of the treacherous Amalekites. Origen (homily 11 on Exodus): “Moses,” he says, “calls [him] JESUS; the Law calls [him] Christ — that he may choose for himself mighty men out of the people. Moses could not choose: but JESUS alone is he who could choose mighty men — [he] who said: ‘You have not chosen me, but I have chosen you.’ For he himself [is] the Leader of the chosen, he [is] the prince of the mighty, he [is] the one who fights with Amalek. For he it is who enters into the house of the strong one, and binds the strong one, and plunders his vessels.” More briefly, into the same opinion, Theodoret (question 34 on Exodus): “JESUS,” he says, “preserved a trophy of a name shared with our Saviour — both in that he obtained this appellation, and because of this: that he made use of the work of chosen men, just as CHRIST [made use] of the ministry of the sacred Apostles.”