1 Kings 22:11
And Zedekiah the son of Chenaanah made him horns of iron: and he said, Thus saith the LORD, With these shalt thou push the Syrians, until thou have consumed them. And Zedekiah the son of Chenaanah made him horns of iron: and he said, Thus saith the LORD, With these shalt thou push the Syrians, until thou have consumed them.
The iron horns were made as a sign of a confident assurance that Ahab would push the Syrians at Ramoth-gilead until they were consumed and win the battle. That promise was given in a setting where Ahab was opposed to Micaiah because Micaiah prophesied evil against him, so the confident word of victory stood alongside a rejected warning. Against it stood Micaiah's warning that Israel would be scattered as sheep without a shepherd, without a leader. Both kings ignored that warning and went up, Ahab died in the battle, and the result exposed the assurance of victory as false.