Editor’s Note: Please see previous works from our “Weapons of War” series including: Five NATO Weapons of War Russia Should Fear, Five Russian Weapons of War NATO Should Fear, Five Chinese Weapons of War America Should Fear, Five American Weapons of War China Should Fear, Five Japanese Weapons of War China Should Fear, Five Best Weapons of War from the Soviet Union and Five Taiwanese Weapons of War China Should Fear.

Israel has its hands full at the moment in Gaza. But Gaza’s rockets aren’t the only thing that keep Israeli strategists up at night. Last week, the nuclear talks between Iran and the P5+1 were extended into late November. A deal is still a very real possibility. But failure is, too. There’s broad agreement across the Israeli political spectrum that letting Iran get the bomb is an unacceptable risk. Many in the Israeli national-security establishment, particularly around Prime Minister Benjamin Netanyahu, have entertained the notion of an Israeli strike on Iran’s nuclear facilities if diplomacy fails and Iran makes a move toward the bomb. Iran would surely retaliate.

(This first appeared in 2014). 

Iran has a problem, though. If you’ve looked at a map lately, the Islamic Republic doesn’t share a border with the Jewish state. They’re more than 550 miles apart at their closest, and the two countries’ cores are nearly one thousand miles apart. That’s a big challenge for Israel, whose powerful air force would have to fly to the limits of its range just to reach Iran’s nuclear facilities. But it’s a bigger challenge for Iran, whose air force, held back by decades of sanctions, is far too feeble to break into Israel’s well-defended airspace.

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Iran’s response to these challenges has been to develop a range of tools, many of them underhanded, that would allow it to hit Israel back. But not all weapons are created equal. Prior lists in our “Five Weapons” series have tried to rank weapons systems not just by how advanced they are or how widely they were used. After all, an advanced weapon might be too expensive and draw resources away from other systems, reducing overall military effectiveness (see Germany in the Second World War). A ubiquitous system might not be very good, also cutting its utility. And a weapon that doesn’t have a good crew behind it might as well not be good. But so many of Iran’s tools are highly asymmetric and highly secretive. Their impact on the strategic balance is the only criterion we can rely on. So what can Iran count on to mitigate the risk of an Israeli strike—and to hurt Israel if it does attack?

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5. Iran’s Palestinian Proxies

Iran always tries to take the toughest line in the Muslim world in its support for Palestine. Tehran is a key supporter of rejectionist elements that refuse to recognize Israel and are ready to take up arms against it. Iran’s traditional best buddy in this has been Hamas. Hamas’ control of the Gaza Strip and its growing rocket capabilities—they’ve shown they can hit Tel Aviv—make it a difficult foe. But events in Syria seriously damaged Iran’s relationship with Hamas—the Sunni Palestinian group didn’t like watching Iran back the Alawite Bashar al Assad to the hilt as he brutalized the heavily Sunni opposition. Iran cut off the tens of millions of aid it sends to Hamas each month—and Hamas answered by announcing that it would not become involved in a conflict between Iran and Israel. But things turned south fast for Hamas when Mohamed Morsi’s government was overthrown in Egypt. Hamas is aligned with the Muslim Brotherhood, so Morsi was a kindred spirit. The virulently anti-Brotherhood Sisi government, not so much. Egypt’s taking a much harder line toward Hamas now, including by cracking down on its lucrative networks of smuggling tunnels. This pushed Hamas back into Iran’s arms.

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But how much of a hammering would Hamas be willing to take on Iran’s behalf? Not so clear. That’s why Iran has sought ties with Palestinian movements more extreme than Hamas, chiefly the Palestinian Islamic Jihad (PIJ). PIJ has rockets and fighters and a long history with Iran. It’ll be a more reliable ally than Hamas. Yet with both militias, a question remains: How much of an impact can they have? The current conflict has shown that Israel’s Iron Dome missile-defense system can catch most of the Palestinians’ rockets.

Of course, Israel still isn’t safe in these conditions, and has been drawn into ground operations. That’s what Iran wants in the event of a conflict. Yet the Iron Dome gives Israel the ability to juggle priorities more efficiently. If it’s also facing, say, a major bombardment from Hezbollah in the north, and feels it needs to go in on the ground in both Lebanon and Gaza, the Iron Dome might allow Israel to fight one ground war at a time, leaving the Palestinians on the back burner while it goes after Hezbollah first.

The unknown here is Iran’s capabilities to cause trouble in the West Bank. Israel’s extensive military and settler presence in the West Bank presents a ripe target, and the West Bank is closer to Israel’s core, too. Nothing massive is likely, but Iran would hope to draw at least some blood and divert at least some Israeli effort there.

4. Terrorists and Spies

Iran has extensive networks of spies, smugglers, money launderers and worse around the globe—including in places you wouldn’t expect, like South America and Canada. One of the more odious elements of Iran’s foreign policy—well, before it was a major backer of Bashar al Assad’s urban demolition, torture  and asphyxiation campaign in Syria and before one of Tehran’s proxies in Iraq was committing massacres—was its willingness to use those networks to attack Israeli diplomats and, worse, to treat non-Israeli Jews as proxy targets when it didn’t feel like going after Israelis. This was the case in Argentina, when friends of the Islamic Republic bombed Israel’s embassy (1992, twenty-nine dead) and a Jewish community center (1994, eighty-five dead). Similar attacks—fortunately with no deaths—followed eight days later in London. And these were not isolated incidents. After Israel was apparently involved in the assassination of several Iranian nuclear scientists, Israeli diplomats were targeted in Tbilisi, Georgia and New Delhi, India in February 2012, with the wife of Israel’s military attache to India being seriously injured. A similar attack in Thailand failed, apparently due to the incompetence of the attackers; that July, a suicide attack by apparent Hezbollah operatives on a busload of Israeli tourists in Bulgaria killed six innocent people. And alleged Iranian plots have been uncovered around the world in recent years, including (most alarmingly) a 2011 plot to assassinate the Saudi Arabian ambassador to the United States in a swank Washington, D.C. restaurant—with the convicted terrorist saying “no big deal” when he was told that the attack could have caused 100 or even 150 casualties.

Iran’s operatives abroad aren’t always the most effective or the hardest to detect, and Israel seems particularly effective at stopping Iranian agents from operating inside its own borders. Yet, as the saying about aerial warfare used to go, the bomber will always get through. Lives would be lost around the world in the wake of an attack on Iran. Attacks might occur inside the United States, and would be at Tehran’s discretion in Europe, too. The world’s security services would likely appreciate as much warning as Israel could give them that an airstrike was coming, as that would give them the chance to round up as many Iranian agents within their country as they could find. But they’d be unlikely to get everyone.

3. Ballistic Missiles

Iran has, experts say, “the largest and most diverse ballistic missile arsenal in the Middle East.” Developed with Libyan and North Korean aid, the Iranian missile program now boasts a range of weapons that can reach Israel and many other targets around the region. Iran’s even dabbled with missiles that could hit Western Europe. Iran also has shorter-range missiles that it can deploy against its unfriendly neighbors to the south—particularly Saudi Arabia—and might consider taking potshots at American troops in Afghanistan or American allies further afield, like Jordan. A comprehensive study of a possible Iranian campaign against Saudi oil facilities suggest it wouldn’t be terribly effective. A potshot at the Israeli nuclear facility in Dimona—pulling a page from Saddam Hussein’s playbook—would also be unlikely to achieve meaningful results. But as a weapon of terror, missiles are more useful. A city—like Tel Aviv, for example—is much easier to hit than a reactor core or a refinery tower. Iranian ballistic missiles would be carrying heftier warheads than the ones Hamas is lobbing these days. The Iron Dome system wouldn’t help against big, fast ballistic missiles, and Israel’s Arrow anti-ballistic-missile system hasn’t been put to the test like Iron Dome has. Israeli cities might be tense places under such a bombardment. The real question, however, would be the accuracy and reliability of the missiles and the sustainability of the campaign. If the missiles aren’t finding their targets or Iran doesn’t have many to fire, Israel probably won’t come out of that exchange feeling like a loser.

2. Hezbollah

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?

1. America

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.

Conclusions

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.