Why hasn’t Iran attacked Israel to avenge Hamas’s leader?

Nearly a month has passed since Ismail Haniyeh was assassinated in a Tehran guest house belonging to the Iranian Revolutionary Guard Corps. Iran blamed Israel for the Hamas leader’s death from a remotely denoted explosive, which appears to have been planted nearly two months earlier. Two IRGC operatives were reportedly responsible for planting that explosive.

Despite Israel refusing to confirm or deny that it had a hand in Haniyeh’s death, the Iranian government has vowed revenge. Iran has rejected pleas from both the U.S. and European leaders not to attack Israel, which...