What does Judges 15:9 mean?

In a series of escalating acts of revenge, Samson has brutalized the Philistines in and around Timnah. They may or may not know that he killed thirty men in the fortified city of Ashkelon (Judges 14:19). They certainly know he burned the wheat crops and olive groves around the town of Timnah (Judges 15:5). They've experienced some unspecified, vicious retaliation since then (Judges 15:8).

Now the Philistine army has been called into action. That those sent are "encamped" implies a formal military operation. Their goal is to capture Samson and end him. They set up an army base in the territory of Judah near a place called Lehi. It's unclear if Lehi was a specific a town at that time or if the name was given later. The word Lehi means "jawbone," and a jawbone will feature heavily in what happens next (Judges 15:15).

Samson is hiding somewhere near the border between the territories of the tribes of Judah and Dan. It is the people of Judah, though, who find the Philistine army suddenly encamped to do battle against them.