What does Judges 3:1 mean?

Chapter 3 begins with a reference to a statement made by the Lord at the end of chapter 2, "Because this people have transgressed my covenant that I commanded their fathers and have not obeyed my voice, I will no longer drive out before them any of the nations that Joshua left when he died, in order to test Israel by them, whether they will take care to walk in the way of the Lord as their fathers did, or not" (Judges 2:20–22).

This means God intentionally allowed specific nations to continue to exist in and around Israel—despite having earlier commanded Israel to utterly destroy them (Deuteronomy 20:16–18). This was in response to Israel's failure to complete that task, through indifference and disobedience. Over time, the presence of these depraved nations would "test" Israel's faithfulness. In truth, God already knew exactly what would happen; this "test" is really more of a "demonstration," for the people's own sake.

This verse narrows those God intends to test by using these other nations against His people. He will test all in Israel who had not experienced the wars in Canaan. In other words, these tests are intended for the generations of Israelites who followed the time of Joshua. Joshua's generation experienced war in the great initial conquest of Canaan after the Israelites entered the Promised Land.

The following generations were meant to experience war in driving the remaining Canaanites from the land in each territory, but they had failed to do so. God would now use war to test these new generations, to see if they would return to Him in times of great need, as the previous generations had done when going to war against the Canaanites the first time.