The objections to Pekah being a rival to Menahem usually center on Pekah’s position as an officer in the army of Pekahiah, Menahem’s son and successor (2 Kgs 15:25). But there is nothing inherently unreasonable about two rivals reaching a détente under which one contender accepts a subordinate position, and he then bides his time until the opportunity comes to slay his rival (or his rival’s son) in a coup. Once the rivalry had begun, the external threat (Assyria) provided compelling reasons for a détente.