Judges 6:2

And the hand of Midian overpowered Israel , and because of Midian the people of Israel made for themselves the dens that are in the mountains and the caves and the strongholds .

Because the power of Midian was so oppressive, the Israelites prepared shelters for themselves in mountain clefts, caves and strongholds.

And the hand of Midian prevailed against Israel : and because of the Midianites the children of Israel made them the dens which are in the mountains, and caves, and strong holds.