The answer is: Philistines

1 Samuel 31:9 - After Saul fell on his sword to avoid capture, the Philistines found his body, beheaded him, and displayed his body on the wall of Beth-shan and his head in the temple of Dagon.

When King Saul, the first monarch of Israel, met his tragic end on Mount Gilboa, the Philistines wasted no time capitalizing on the victory. The beheading of Saul was no mere act of violence; it was also about sending a powerful message. By displaying his decapitated body on the wall of Beth-shan and placing his head in the temple of Dagon, they were asserting dominance and celebrating their god, Dagon, over Israel's king. Dagon, often associated with agriculture and fertility, represented a vivid contrast to the Jewish deity, Yahweh.

This incident is notable not just for its brutality but also for its dramatic irony—it reflects the very fate Saul feared when he consulted the medium of Endor out of desperation to speak to the deceased prophet Samuel. Ironically, it’s as if desperation followed Saul to his last moments, sealing his fate in a heart-breaking yet prophetic twist of Hebrew history.

Moreover, Philistine treatment of Saul was reflective of traditional warfare in the ancient Near East, where the defeated must become a cautionary example to others. This echoes other historical references in the Bible, including threats to enemies' bodies (think of Goliath's severed head making its way through ranks—possibly a trial of strength and glory for David).

Saul’s posthumous humiliation encapsulates not only a turning point in Israel's history but also a moment that reminds viewers of consequences in life driven by pride, unwise choices, or desperate pleas for peace.