What does Judges 21:17 mean?

In the previous chapter, not long before this moment, the leaders of Israel were deeply committed to wiping the tribe of Benjamin from the face of the earth. While God called on them to enact justice (Judges 20:28), He did not tell them to nearly obliterate the entire tribe (Judges 20:47–48). The other eleven tribes raged through the territory and eliminated all but six hundred men. They also made a foolish promise to never give their daughters as wives to Benjaminites. To work around that vow, the nation attacked the only clan who hadn't supported the war, giving those women to the tribe of Benjamin. Guilt for protecting the sinful city of Gibeah (Judges 20:11–13) has been repaid many times over, but about one third of the surviving men still have no wives.

Benjamin's inheritance of land and borders under the promise of God must be preserved for those who survived that terrible day of battle. Now—well after making foolish promises and wreaking excessive havoc—Israel wonders how Benjamin can possibly keep their own territory if their numbers remain so small? The Israelites are urgent to find more wives so the tribe can repopulate as quickly as possible.