Judges 6:2
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. 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.
The hand of Midian prevailed against Israel and brought the people into subjection, though Israel might through God have subdued Midian itself. Because of the Midianites the Israelites left their homes in the open country and made for safety walled towns, fortresses, mountain dens, caves, and rocky strongholds. Midianite raiders stripped the land and the fields of their harvests, returning year after year and leaving the people facing hunger.
This oppression lasted seven years. Israel's sins separated them from God, so His strength and protecting hand were withdrawn and they could no longer prevail against their enemies. The verse belongs to the repeated story of backsliding and chastisement followed by confession and deliverance, in which God did not utterly forsake His people but kept a remnant true to Him and from time to time raised up faithful and valiant men to put down idolatry and deliver Israel from its oppressors.