What does Judges 10:15 mean?

The people of Israel have confessed their sin in serving false gods and forsaking God (Judges 10:6–10). They expect Him to save them as He has done in the past. Surprisingly, He has refused. Instead, the Lord sarcastically told them to turn to their false idols for help (Judges 10:11–14). This rejection is not absolute, or final, however—it's meant to make a crucial point. God knows Israel has not reached the point of true repentance. They have expressed regret and a desire to be rescued, but they've done nothing consistent with repentance (2 Corinthians 7:10). As the next verse explains, they had not yet even put away the false gods and idols from their homes.

Now the Israelites respond to the Lord with another confession, phrased more bluntly and backed up with action. They confess once more that they have sinned. They acknowledge that they deserve the Lord's punishment. Israel also acknowledges God's sovereignty, accepting that He can—and will—do as He sees fit. Even so, they make a heartfelt plea to be rescued from the Ammonites and the Philistines. They bring this request with humility, making no excuses and offering no resistance to the Lord's purposes.

Most importantly, the people will do something which demonstrates that their repentance is real (Judges 10:16).