John assassinated King Ahab and assumed the kingship of Israel. Then he had all of Ahab’s sons killed to eliminate all claimants to the throne. These sons were beheaded, and their heads were piled in a heap outside the entrance to the city of Jezreel. King Ahab’s palace was located at Jezreel. This was probably Jehu’s way of sending a message that anyone who remained loyal to Ahab and opposed Jehu’s accession to the throne would suffer the same fate.
Execution by decapitation was common in the Old Testament times. David killed Goliath by cutting off his head (1 Samuel 17:51). King Saul was beheaded by the Philistines (1 Samuel 31:9). But she masters of decapitation were the Assyrians. Monuments discovered in excavations at their capital city of Nineveh depict the heads of hundreds of captives piled up outside the city gate.
1 KINGS 10:8 – There came a messenger, and told him [King Jehu], saying. They have brought the heads of the king’s sons. And he said, Lay ye them in two heaps [Put them in two piles, NIV] as the entering in of the gate until the morning.