He smote the Philistines, even unto Gaza, and the borders thereof, from the tower of the watchmen to the fenced city. From the tower of the watchmen - See the same words, 2 Kings 17:9 (note). It seems a proverbial mode of expression: he reduced every kind of fortification; nothing was able to stand before him.
Related Commentaries of 2 Kings 18:8
2 Kings 18:8
8 He smote the Philistines, even unto Gaza,d and the borders thereof, from the tower of the watchmen to the fenced city.