Aside from a potentially game-changing American intervention that shapes the fate of Iran’s nuclear program, two factors will help decide the length of the Israel-Iran war: Israel’s reserve of missile interceptors and Iran’s stock of long-range missiles.

Since Iran started retaliating against Israel’s fire last week, Israel’s world-leading air defense system has intercepted most incoming Iranian ballistic missiles, giving the Israeli Air Force more time to strike Iran without incurring major losses at home.

Now, as the war drags on, Israel is firing interceptors faster than it can produce them. That has raised questions within the Israeli security establishment about whether the country will run low on air defense missiles before Iran uses up its ballistic arsenal, according to eight current and former officials.

Already, Israel’s military has had to conserve its use of interceptors and is giving greater priority to the defense of densely populated areas and strategic infrastructure, according to the officials. Most spoke on the condition of anonymity to speak more freely.

President Trump’s decision to defer an American attack on Iran has left Israel in a strategic bind.

Israel’s main remaining war goal is to wipe out a nuclear enrichment site at Fordo in northern Iran, which is buried so deep underground that Israeli bombs will struggle to damage it.

For days, Israeli officials hoped that Mr. Trump would send American warplanes armed with the only munitions in the world that are deemed powerful enough to destroy Fordo.

Now, Mr. Trump says he will wait up to two weeks before deciding whether to make such an intervention — a delay that imposes a dilemma on Israel.

The longer Israel waits for Mr. Trump, the greater the strain on its air defense system. To keep out Iran’s ballistic missile barrages, Israel is burning through its stocks of missile interceptors, forcing it to prioritize the protection of some areas over others. As time goes on, that raises the risk of more missiles hitting both civilian neighborhoods and strategic security sites.

With Israel’s airspace closed and much of its economic life suspended, the war’s protraction will also come at an economic cost. The sooner the war ends, the faster commercial flights will return and businesses can resume full operations.

Rather than wait for American help, Israel could decide to attack Fordo alone — taking a chance with the planes and munitions it has at its disposal. Some analysts say that Israel could even send commandos to enter and sabotage the site. Prime Minister Benjamin Netanyahu hinted at going it alone on Thursday, saying in a television interview that Israel would “achieve all of our objectives, all of their nuclear facilities. We have the power to do so.”

But experts say that this route is fraught with risk and that its effect may be limited. “It probably won’t be on the scale of what the U.S. can achieve,” said Itamar Rabinovich, a former Israeli ambassador to Washington. “If we could do what the U.S. can, we would have already done it.”

Another option is for Israel to wind down the war unilaterally, without attacking Fordo. But that approach would leave at least a significant part of Iran’s nuclear enrichment program intact, leaving open the possibility that Iran might create a nuclear bomb that could be used against Israel.

For now, Israel does not seem set to take that route. Israel’s political leadership has begun to speak explicitly about prompting the collapse of the Iranian regime and assassinating its leader, Ayatollah Ali Khamenei. Even if Israel has no real way of toppling his government, the tone of the comments suggest that Israel, at the very least, intends to continue with its strikes for several days.

The tone of the Israeli news media on Friday also indicated continued domestic support for the Israeli campaign, as did new opinion polling. After Israel’s attack on Iran, Mr. Netanyahu’s party is in its strongest polling position since October 2023, when Hamas carried out the deadliest attack in Israel’s history.

Lia Lapidot contributed reporting from Tel Aviv.

Over the past week, Israel has pummeled Iran with airstrikes and Iran has sent barrages of ballistic missiles and drones toward Israel. At least 24 people in Israel and 224 people in Iran have been killed in attacks since June 13, their governments have reported. Israel’s sophisticated air defense system has in the past fended off attacks from Gaza, Lebanon, Iraq, Syria, Yemen and Iran. Still, Iranian missiles have tested the multilayered network, and some projectiles have made impact. A strike on Thursday wounded about 80 people at the Soroka Medical Center in Beersheba, the largest hospital in southern Israel, and caused extensive damage.

The Israeli defenses include the Iron Dome, which was designed to stop short-range rockets and artillery such as those fired from Gaza. Two other systems, David’s Sling and Arrow, are designed for medium- and long-range threats, including planes, drones, rockets and missiles. (The U.S. military has also helped Israel intercept incoming Iranian missiles, U.S. and defense officials told The Washington Post. The officials spoke on the condition of anonymity to discuss ongoing operations.)

Advertisement

An Israeli military official told reporters Tuesday that Iran had fired over 1,000 projectiles since June 13, and a few dozen have made impact in Israel. He spoke on the condition of anonymity in line with Israeli military rules.

Here’s what to know about Israel’s air defense system.

Iron Dome

A centerpiece of Israel’s air defense is the Iron Dome, developed by the Israeli firm Rafael Advanced Defense Systems and Israel Aerospace Industries and put into service in 2011. It is designed to stop the short-range rockets and artillery fired by Hamas, Islamic Jihad and other groups.

The Iron Dome relies on radars and analysis to determine whether an incoming rocket is a threat. If there’s a danger to a populated area or important infrastructure, it fires an interceptor.

The interceptors, which may be fired vertically from mobile units or a static launch site, detonate the incoming rocket in the air.

Advertisement

Rockets, which can cost as little as a few hundred dollars, are often crude and lack guidance systems. Each Iron Dome interceptor that is fired costs about $80,000, Israeli media outlets have reported.

Israeli officials and defense companies have said the Iron Dome has a success rate of more than 90 percent. Some defense analysts question those numbers against evolving threats.

President Donald Trump said in May that the United States would begin building its own “Golden Dome” missile defense system to intercept projectiles fired not just from other countries but also from space.

Trump estimated its cost at $175 billion. The Congressional Budget Office estimates that deploying and operating just the space-based interceptors of such a system could cost from $161 billion to $542 billion over the next two decades.

David’s Sling

David’s Sling is designed to intercept ballistic and cruise missiles and medium- to long-range rockets.

Advertisement

Developed by Rafael Advanced Defense Systems and Raytheon, a major U.S. defense contractor, it counters rockets and missiles fired at a range of 25 to 186 miles. It has been operational since 2017.

Arrow

The Arrow 2 and 3 systems are the top level of Israel’s air defense network. They are designed to intercept missiles that fly outside Earth’s atmosphere. Arrow missiles cost about $3 million each.

The Arrow 2 uses explosives to destroy its targets. The Arrow 3, jointly funded and developed with the U.S. and completed in 2017, does not — it relies instead solely on the damage caused by the interception itself.

How effective is Israel’s defense system against Iranian attacks?

Israel says the majority of Iranian missiles are intercepted, but its military warns Israelis that their “conduct in the home front is critically important,” including sheltering in protected spaces when emergency sirens blare. “We cannot afford to be complacent,” Israel Defense Forces spokesperson Effie Defrin said Tuesday. “The Iranians still possess the capabilities and intent to strike Israel’s home front.”

Advertisement

The Israeli government on Tuesday reported an interception success rate of more than 90 percent.

Iran’s ballistic missiles can travel the more than 1,000 miles between Iran and Israel in 12 minutes. They’re propelled into Earth’s outer atmosphere and beyond by rockets and then turn back toward Earth to descend at several times the speed of sound — thousands of miles per hour.

Iran has also launched cruise missiles, which propel themselves throughout their flights, and drones programmed to carry explosives toward predetermined targets.

Iran’s military on Tuesday claimed it was also using “new and advanced weapons.”

Israeli Prime Minister Benjamin Netanyahu said Monday that “Israel controls the skies over Tehran.” The IDF has significantly degraded Iran’s attack capabilities by striking missile launchers, drone storage facilities, and missile production and storage sites.

Advertisement

In October, Iran sent at least 180 ballistic missiles toward Israel. A Washington Post analysis found that at least two dozen made it through Israeli defenses. Some caused damage at or near Israeli military and intelligence sites.

Iran’s capabilities in that attack surprised some analysts, who said they had not known Iran had the number of launchers it required. Now, however, analysts say its capabilities might be waning as it uses up its stock.

Patriot and THAAD missile defense batteries, operated by U.S. military personnel and originally deployed under the Biden administration, also participated in the Israeli air defense on June 13, according to U.S. defense officials, who spoke on the condition of anonymity to discuss operations. That represented a more limited participation in Israel’s defense than last year, when American air and sea assets helped shoot down incoming Iranian missiles during two retaliatory Iranian attacks.

Advertisement

It is a week since Israel began its largest attack ever on Iran, and in conventional military terms it is clear that Tehran is under extreme pressure. Israel has been able to achieve superiority over Iran’s skies at extraordinary speed, within hours of launching its surprise assault. Its military claimed on Monday to have knocked out 120 Iranian air defence systems through a mixture of air and drone strikes – about a third of Tehran’s pre-war total.

In response, Iran’s most effective weapon has been its stock of high-speed ballistic missiles, estimated at about 2,000 by Israel’s Defense Force (IDF) at the outset of hostilities last week. But the heavy targeting by Israel of launch sites in western Iran, in underground bases such as at Kermanshah – coupled with Israel’s grimly effective targeted killing of Iran’s top military commanders – have left Iran struggling to respond militarily and presenting a significant threat.

Iran has so far launched more than 400 missiles at Israel, but half, about 200, were launched in the initial retaliatory barrages last Friday. Since Monday the size of its missile barrages has reduced to a maximum of 15 to 20 (including 15 on Thursday afternoon), compared with up to 40 during the weekend, according to a count compiled by a US thinktank, the Institute for the Study of War. Iran’s ability to manufacture new weapons is also likely to be limited, estimated by the US to be 50 a month before the hostilities broke out.

The sheer speed of ballistic missiles makes them dangerous weapons and a number – about 10% – continue to evade Israel’s sophisticated air defences, including a strike on the Soroka Medical Center in the southern city of Beersheba on Thursday that wounded 76. But the munitions mostly do not appear to be effectively targeted at Israel’s military-industrial complex, aside from an attack on the refinery at Haifa in northern Israel on Sunday that led to the shutting down of the facilities there.

Intercepting ballistic missiles is primarily the task of Israel’s newest air defence system, Arrow 3, which have a 1,500-mile range and can knock out incoming missiles beyond the Earth’s atmosphere, and its predecessor Arrow 2, though the US has been providing help with a Thaad system and destroyers based in the eastern Mediterranean. Neither Arrow system is cheap – the cost of an Arrow 3 interceptor has been put at $3.5m, though other estimates suggest a figure of $2m, and $1.5m for Arrow 2. The Israeli business newspaper Globes has suggested that the total cost to Israel of Arrow interceptors has been $1bn to $1.5bn since October 2023.

A key question, however, is how many interceptors does Israel’s military have available – worries compounded by a report in the Wall Street Journal, which cited an anonymous US official as saying that Israel was running low. Stock levels are kept secret and Israel, well aware of the Iranian ballistic missile threat, is considered unlikely to have chosen to attack Iran without at least enough interceptors to match its assessment of the likely threat. Nevertheless, sophisticated defensive missiles take time to manufacture, a problem long revealed in Ukraine, where Russia continues to fire more missiles than Kyiv has available air defences.

In less than a week, Israel has told allies that it is further ahead in its attack than it expected to be, having killed 21 out of 22 senior military figures in the first 24 hours, and 10 out of 12 nuclear scientists. The country’s jets face almost no air defence threat as they fly over western and central Iran – Israel has so far acknowledged the loss of one drone – meaning they are able to target sites in the country with apparent impunity. Even if Israeli stockpiles of attack missiles run down in the next week or two, and there is no US intervention, its air dominance means it can continue to attack at a slower rate.

Iran’s capabilities have been “exposed as inefficient”, concluded the missile analyst Fabian Hinz in a paper for the International Institute of Strategic Studies, while the “Israeli leadership, at least for the time being, [is] accepting the risks of ballistic missile strikes on its population centres”. As Hinz puts it, the “deterrence balance” between the two countries is unravelling – and it may only change back in Tehran’s favour if a suddenly a greater number or higher proportion of its remaining ballistic missiles strike population centres or key sites in Israel. There is no sign of that yet.