Judges 3:1–2

Now these are the nations that the Lord left, to test Israel by them, that is, all in Israel who had not experienced all the wars in Canaan. It was only in order that the generations of the people of Israel might know war, to teach war to those who had not known it before.

These are the nations the Lord left to test all those Israelites who had not experienced any of the wars in Canaan (he did this only to teach warfare to the descendants of the Israelites who had not had previous battle experience):

These are the nations the Lord left in order to test all those in Israel who had experienced none of the wars in Canaan. This was to teach the future generations of the Israelites how to fight in battle, especially those who had not fought before.

These are the nations that the Lord left in the land to test those Israelites who had not experienced the wars of Canaan. He did this to teach warfare to generations of Israelites who had no experience in battle.

These are the nations that Yahweh left, to test Israel by them (that is, to test all those who had not experienced any of the wars of Canaan, in order that the generations of Israel would know war, to teach those who had not experienced it before):

Now these are the nations which the Lord left, to prove Israel by them, even as many of Israel as had not known all the wars of Canaan; Only that the generations of the children of Israel might know, to teach them war, at the least such as before knew nothing thereof;