Only that the generations of the children of Israel— The sacred writer having declared in the former verse the reason why certain of the Canaanites were left, namely, to prove the Israelites; and also who of the Israelites were thus to be proved, namely, that generation which was born after the taking of Palestine; proceeds in the present verse to give another reason why the Canaanites were spared. The verse would be better rendered thus, after Houbigant: and by this means it came to pass that that generation of the children of Israel might learn war, because they had before known nothing thereof. Had no enemies remained, the children of Israel would have given themselves up wholly to the arts of peace, and would have totally forgotten the art of war: but thus they were taught to neglect nothing necessary for their defence; happy had they not neglected what was of the greatest consequence, their allegiance to the Lord of Hosts.
Related Commentaries of Judges 3:2
Judges 3:2
2 Only that the generations of the children of Israel might know, to teach them war, at the least such as before knew nothing thereof;