Judges 1:4
And Judah went up; and the LORD delivered the Canaanites and the Perizzites into their hand: and they slew of them in Bezek ten thousand men. And Judah went up; and the LORD delivered the Canaanites and the Perizzites into their hand: and they slew of them in Bezek ten thousand men.
The verse belongs to the introduction to the book found in chapters 1 and 2 and 3:1-6, which shows that Israel had not yet possessed all of the country. That introduction comes sometime after the death of Joshua and opens a new period in Israel's history after bitter enslavement and oppression. This unfinished possession was because Israel failed to carry out the instructions God had given.
The same introductory section deals with Israel's consequent captivity and with the help that came to them through the judges, or saviours, whom the Lord raised up on their behalf. The judges were defenders of a cause raised up in times of crisis to contend for the independence of the people and to judge in the administration of law. In this new setting Israel was free to choose between obedience and self-will and thereby to shape its national life and character.