The Lebanese Shia militia is one of revolutionary Iran’s oldest and truest friends. It’s long been willing to carry out deadly attacks in third countries on Iran’s behalf, and it’s proven itself to be an increasingly effective fighting force. Hezbollah’s crowning achievement was holding its own in its 2006 war with Israel—a war touched off when Hezbollah forces ambushed Israeli forces just inside Israel’s own borders, killing several and capturing two more. Israel launched attacks into Lebanon, and its troops were surprised by Hezbollah’s tactical and technological sophistication. A Hezbollah antiship missile even scored a deadly hit on a small Israeli Navy ship lingering off Lebanon’s coast. The latter incident couldn’t have happened without a number of Israeli errors—but it was nonetheless a major publicity victory for Hezbollah. The rest of the war, even more so. Hezbollah leader Hassan Nasrallah shot to popularity around the Middle East as the first Arab leader who could claim to have fought a war with Israel and not lost.
A few things have changed since then. Hezbollah has gotten sucked into the conflict in Syria, bleeding its resources and critically wounding its reputation in the non-Shia world. Hezbollah’s most effective terrorist operative, Imad Mughniyah, was assassinated. But more importantly, Iran has continued to arm and train the militia. Israel now says that Hezbollah has tens of thousands of missiles in its arsenal and an extensive network of facilities throughout southern Lebanon that will be useful in launching those missiles and fighting any Israeli ground forces that come in to stop them. Israel has had to fight to keep relatively advanced systems out of that massive arsenal. The IAF has repeatedly carried out airstrikes against targets inside Syria that appeared to be involved in shipping high-tech systems to Hezbollah: the Fateh-110 ballistic missile, Iran’s solid-fueled and apparently relatively accurate answer to the Scud; the SA-17 surface-to-air missile, a more advanced version of the system that apparently shot down a Malaysian airliner over Ukraine; and the Yakhont, a rangy, supersonic antiship missile much more capable than the one that struck the Israeli corvette in 2006. Estimates vary on just how effective Israel’s interdiction campaign has been—they’ve certainly destroyed or damaged a lot of expensive hardware, but they might not have created an airtight seal. Each system would make Hezbollah a tougher nut for Israel to crack—the Fateh-110 allowing Hezbollah a better chance of hitting Israeli military bases, the SA-17 testing the IAF’s countermeasures and possibly forcing tactical adjustments, and the Yakhont hindering close-in naval operations, threatening shipping in the region, and even putting Israel’s increasingly important offshore natural-gas facilities at risk.
But even without new toys, Hezbollah’s rockets are Iran’s best chance to inflict serious physical damage on Israel, to terrorize Israeli cities and to draw Israeli ground troops into a tough confrontation. Hamas is scary, but Hezbollah remains a categorically different threat. There is one big question mark, however. How much has Hezbollah’s involvement in Syria weakened the organization as a fighting force?
One of the biggest losers in an Israeli attack on Iran will be the United States. A large-scale Iranian retaliation might include extensive attacks on America’s bases and allies in the region and, most alarmingly, on the flow of oil out of the Gulf. Iran can’t stop that oil flow, or if it does, it can’t for long. But it can cause a major spike in oil prices, and if it sustains the conflict it could keep them high. That would cause significant economic damage around the world, potentially enough to tip the global economy back toward recession after a few years of feeble recovery.
These high costs mean the United States would almost certainly be forced to join the war. Accordingly, preventing an Israeli attack has been a key goal of U.S. Iran policy. But the aftermath of an Israeli attack wouldn’t just be harmful to America. It could do serious damage to the U.S.-Israeli relationship. Would Barack Obama’s testy relationship with Benjamin Netanyahu get better if Obama felt Netanyahu had made a massive, legacy-wrecking mess for him to clean up? Would the American public’s support for Israel—weaker among young people and minorities and in growing danger of becoming a partisan issue—take a big hit if Americans saw their gas prices going up and their soldiers dying and felt that Israel had started it? None of this is a foregone conclusion. Israel would hopefully give some warning that an attack was on the way, which could give the United States a chance to scramble into a defensive posture. Iranian terrorist actions and attacks on American troops would provoke public outrage toward Tehran, not Tel Aviv. If Washington felt the diplomatic path was dead, or if the attack was provoked by Iran expelling nuclear inspectors, the damage would also be lessened.
But this would still be the toughest moment in U.S.-Israeli relations in a generation. All sides would have opportunities to make damaging mistakes and misinterpretations. And if the Israeli public came to feel that much of the damage to Israel’s most important relationship was avoidable, the prime minister could lose his post.
Tehran knows all of this, and can increase its deterrent by heightening the risks to the U.S.-Israeli relationship. However, it also knows that attacking America and others in the wake of an Israeli airstrike carries great risks of its own. Iranians have sacrificed a lot for those nuclear facilities. Their destruction would create a very volatile moment in Iran’s politics. Bringing America—a far deadlier enemy than Israel—into the war would double down on the crisis. The destruction in Iran could be much more widespread, and any nuclear facilities that had survived Israel’s strike would suffer a second, more powerful blow. That probably won’t be enough to stop Iran from widening the war. Israel’s leaders will have to think very hard about the danger to their relationship with the United States before they launch an attack.
There are a few other tools at Iran’s disposal that are worth mentioning. Iran has dabbled in cyber warfare and might have some surprises in store on that front. Iran’s extensive militia presence in Iraq and Syria might have some part to play—perhaps launching rockets into the Golan Heights or at American facilities in Baghdad. The insecurity in Egypt’s Sinai Peninsula leaves Iran with the potential to launch rocket attacks on the southern city of Eilat from inside Egypt. And Iran might push for more Shia activism and violence in its Gulf neighbors, particularly Bahrain and Saudi Arabia’s oil- and Shiite-rich Eastern Province.
Israel has the ability to weather all of these threats. The choice remains in its hands. But Iran is strong enough, well-armed enough, creative enough, and amoral enough to make the choice a very difficult one.