With Israel’s killing of Hezbollah leader Hassan Nasrallah, the wars in the Middle East have hit a turning point—though it’s hard to say what direction they’ll now take: toward some uneasy equilibrium or an escalation in the fighting. Historians and strategists disagree over whether a “decapitation” attack—the assassination of a leader—has much effect on the course of a war. But Israel’s recent tactics have gone well beyond decapitation. As a prelude to the bombing of an apartment complex just...