only that the generations of the children of Israel might know, to teach them war, at the least such as beforetime knew nothing thereof:

That afterwards their children might learn to fight with their enemies, and to be trained up to war:

it was only that the generations of the people of Israel might know war, that he might teach war to such at least as had not known it before.

(only for the sake of the generations of the sons of Israel's knowing, to teach them war, only those who formerly have not known them),

Only because of the generations of the children of Israel, for the purpose of teaching them war--only those who up till then had no experience of it;

so that afterward their sons might learn to contend with their enemies, and to have a willingness to do battle:

That - Israel might know, to teach them war - This was another reason why the Canaanites were left in the land, that the Israelites might not forget military discipline, but habituate themselves to the use of arms, that they might always be able to defend themselves against their foes. Had they been faithful to God, they would have had no need of learning the art of war; but now arms became a sort of necessary substitute for that spiritual strength which had departed from them. Thus Gods in his judgments leaves one iniquitous nation to harass and torment another. Were all to turn to God, men need learn war no more.

Only that the generations of the children of Israel might know, to teach them war, at the least such as before knew (b) nothing thereof;
(b) For they trusted in God and he fought for them.

Only that the generations of the children of Israel might know and teach them war,.... That is, the following nations were left in the land, that the young generations of Israel might by their wars and conflicts with them learn the art of war, and be inured to martial discipline; which, if none had been left to engage with, they had been ignorant of: besides, their fathers in Joshua's time, as Jarchi and Kimchi observe, had no need to learn the art of war, for God fought for them; they did not get possession of the land by their own arm, and by their sword, but by the power of God in a miraculous way; but now this was not to be expected, and the Canaanites were left among them to expel, that they might be trained up in the knowledge of warlike affairs, and so be also capable of teaching their children the military art; which they should make use of in obeying the command of God, by driving out the remains of the Canaanites, and not give themselves up to sloth and indolence; though some think that the meaning is, that God left these nations among them, that they might know what war was, and the sad effects of it; and the difference of fighting with their enemies alone, as other men, and the Lord fighting along with them, and for them, as he did for their fathers:
at least such as before knew nothing thereof; being either unborn, or at an age incapable of bearing arms, or learning the art of war.

Teach them war - That by the neighbourhood of such warlike enemies, they might be purged from sloth and security, and obliged them to innure themselves to martial exercises, and to stand continually upon their guard, and consequently to keep close to that God whose assistance they had so great and constant need of.