Gaza indicates the extreme point south to which they spread their devastations, crossing the Jordan near Bethshan (Scythopolls), and entering by the valley of Jezreel, and sweeping along the whole of the maritime plain or Shephelah.
Related Commentaries of Judges 6:4
Judges 6:4
4 And they encamped against them, and destroyed the increase of the earth, till thou come unto Gaza, and left no sustenance for Israel, neither sheep, nor ox, nor ass.