Albert Barnes Commentary 1 Samuel 28:4

"And the Philistines gathered themselves together, and came and encamped in Shunem: and Saul gathered all Israel together, and they encamped in Gilboa." — 1 Samuel 28:4 (ASV)

Gilboa - Now called Jebel Fukuak. But the ancient name is preserved in the village of Jelbon, situated on the south side of the mountain. It was separated from Shunem (see the marginal reference) by the deep valley of Jezreel. The Philistines either advanced along the seacoast, and then entered the valley of Jezreel from the west, or they came by the present road right through Samaria, starting from Aphek (1 Samuel 29:1).