“Then the sons of Israel did what was evil in the sight of the Lord; and the Lord gave them into the hands of Midian seven years” (Judges 6::1, NASB).
After the time of the conquest of Canaan by the Israelites, each of the tribes settled in the land allocated to them. Since, the Israelites had not completely conquered or subdued all the various Canaanite people-groups as a nation, it was left to the tribes to fight against the Canaanites still remaining in the land they occupied.
The Israelite tribes often formed regional alliances among themselves to fight against the Canaanites. And the Canaanites often formed coalitions with one another and with people groups surrounding the land of Canaan to fight against the Israelites.