Rockets, many carrying tons of TNT, would rain on Israel; drones armed with payloads would crash into crucial facilities, military and civilian. During the Second Lebanon War, in 2006, the rate of such fire reached between 200 and 300 projectiles a day. Today, it might reach as high as 4,000. The majority of the weapons in Hezbollah’s arsenal are standoff missiles with fixed trajectories that can be tracked and intercepted by Israel’s Iron Dome system. But Iron Dome is 90 percent effective on average, meaning that for every 100 rockets, 10 get through, and the seven operational batteries are incapable of covering the entire country. All of Israel, from Metulla in the north to the southern port city of Eilat, would be in range of enemy fire.

But precision-guided missiles, growing numbers of which are in Iranian arsenals, pose a far deadlier threat. Directed by joysticks, many can change destinations mid-flight. The David’s Sling system, developed in conjunction with the United States, can stop them—in theory, because it has never been tested in combat. And each of its interceptors costs $1 million. Even if it is not physically razed, Israel can be bled economically.

First, though, it would be paralyzed. If rockets fall near Ben-Gurion Airport, as during Israel’s 2014 war with Hamas in Gaza, it will close to international traffic. Israel’s ports, through which a major portion of its food and essential supplies are imported, may also shut down, and its electrical grids could be severed. Iran has honed its hacking tools in recent years and Israel, though a world leader in cyberdefense, cannot entirely protect its vital utilities. Millions of Israelis would huddle in bomb shelters. Hundreds of thousands would be evacuated from border areas that terrorists are trying to infiltrate. The restaurants and hotels would empty, along with the offices of the high-tech companies of the start-up nation. The hospitals, many of them resorting to underground facilities, would quickly be overwhelmed, even before the skies darken with the toxic fumes of blazing chemical factories and oil refineries.

Israel would, of course, respond. Its planes and artillery would return fire, and the IDF would mobilize. More than twice the size of the French and British armies combined—at least on paper—the IDF can call up, equip, and deploy tens of thousands of seasoned reservists in less than 24 hours. But where would it send them? Most of the rockets would be launched from southern Lebanon, where the launchers are embedded in some 200 villages. Others would be fired from Gaza, where Hamas and Islamic Jihad, both backed by Iran, have at least 10,000 rockets. But longer-range missiles, including the deadly Shahab-3, would reach Israel from Syria, Iraq, Yemen, and Iran itself. This presents a daunting challenge to the Israeli Air Force, which does not possess strategic bombers capable of reaching Iran and must grapple with the advanced Russian anti-aircraft weapons situated in Syria. Israeli ground troops would be forced to move into Lebanon and Gaza, house-to-house, while special forces would be dispatched deep within Syria and Iraq. Israel’s own conventional missiles could devastate Iranian targets.