Israel is bracing for a coordinated attack by Iran and its allies, the Wall Street Journal reported, which would represent the biggest test yet of a multi-layered air defense system that would have expanded far beyond Israel’s vaunted Iron Dome. “Over the past decade, Iron Dome, developed by the United States and Israel, has become the world’s leading system for shooting down short-range rockets, reducing the threat posed by weapons fired by Washington-designated terrorist groups such as Hamas to population centers,” the paper said.

But Iran and Hezbollah’s capabilities in Lebanon are another matter. Iran has drones and ballistic missiles that Iron Dome cannot intercept. Hezbollah also has an arsenal of tens of thousands of mortar shells, rockets, and precision-guided missiles that could overwhelm Israeli defenses.

In response, Israel and the United States have woven a larger air defense system that relies on the capabilities of the Israeli, American and other air forces; the radar systems of neighboring countries; and even Arab states to shoot down Iranian projectiles.

“It’s a whole system that’s synchronized and works like clockwork,” said Yehoshua Kaliski, a senior researcher at the Institute for National Security Studies, a think tank in Tel Aviv, according to the newspaper. He said he believes Israel is relatively well prepared for a major attack.

Much of this is coordinated through Central Command, which is responsible for U.S. military operations in the Middle East. Israel was brought into Central Command’s geographic area in September 2021, giving it greater ability to coordinate with Arab states with which it does not have diplomatic relations. Military activity is coordinated through Central Command’s headquarters in Florida and its main Middle East station in Qatar.

The system was tested on April 13, when the United States, Israel, Jordan, Britain and France shot down an Iranian barrage of more than 300 projectiles (including drones, cruise missiles and ballistic missiles), with an interception rate of 99 percent, according to the US Department of Defense. Only one person was seriously injured in the attack. Iran said it had destroyed key Israeli military targets and was effective in proving its ability to penetrate Israeli defense systems.

This time, U.S. officials are concerned that the Iranian attack could be accompanied by more simultaneous strikes from Hezbollah and Tehran’s other allies in the region, including the Houthis based in Yemen and militias in Iraq, in an attempt to overwhelm Israeli defense systems.

Iran and Hezbollah are expected to attack Israel in response to Israel's assassination of Fouad Shukr, a senior Hezbollah leader in the Lebanese capital Beirut, and Hamas political bureau chief Ismail Haniyeh in Tehran in the early morning of July 31.

“Iran, Hezbollah and Yemen will respond after the assassination of Haniyeh and Shukr and the bombing of Hodeidah,” Hezbollah leader Hassan Nasrallah said Tuesday, referring to an Israeli airstrike in July on a Houthi-held port city in Yemen.

US Secretary of State Antony Blinken said diplomatic efforts were continuing, calling on all parties to ease tensions.

“Over the last few days, we have been in constant contact with partners in the region, and beyond those conversations, we have heard a clear consensus, no one should escalate this conflict,” Blinken said Tuesday. “We have engaged in intensive diplomacy with allies and partners, and we have conveyed that message directly to Iran. We have conveyed that message directly to Israel.”

One of the anticipated difficulties in dealing with a large, multi-front barrage is the need to quickly classify the various targets and determine what to drop as they are being lobbed.

Analysts say Israel's multi-layered air defense system, developed jointly by the United States and Israel, is designed for such a situation — and consists of several parts aimed at countering different types of threats ranging from short-range missiles to more advanced ballistic missiles.

One of the newest systems, David's Sling, covers short-range missiles and drones, and was developed jointly by Israel's state-owned Rafael Advanced Defense Systems and Raytheon's RTX. The crown jewel of this system is Arrow 3, which can intercept long-range ballistic missiles leaving the Earth's atmosphere, while the previous version of the Arrow, known as Arrow 2, is still used for medium- and long-range missile threats.

The Israeli army said that the "Arrow 3" missile was first used in November 2023, when it intercepted a Houthi missile, and that the "David's Sling" missile was first used before the current war on Gaza in May 2023 to intercept a missile launched from Gaza.

Drones are a weak point in Israeli air defenses, especially when they come in swarms, because of their ability to fly low and evade radar systems. A drone launched by the Houthis from Yemen managed to evade Israeli defenses and hit Tel Aviv on July 19, killing one Israeli. Hezbollah also demonstrated on July 9 that it can launch reconnaissance drones that map Israeli cities and installations, including sensitive military sites.

According to the newspaper, "Israel is developing a new system called 'Iron Beam', which uses lasers to shoot down projectiles, and which security experts believe could be effective against drones. The system is not yet operational, but some officials believe it could be ready by 2025."

With Iran and Hezbollah threatening Israel with severe retaliation and Israelis preparing to stay in shelters for long periods and stockpile essential supplies, Israel's air defense system has been put on high alert and the country hopes to match the success of the April interceptions again.

"The first attack broke a psychological barrier in Iran," Tal Inbar, a senior analyst at the US-based Missile Defense Alliance, told the newspaper, adding that both Israel and Iran learned lessons from it.

One reason Israel was so successful in dealing with the April barrage was that it had several hours of intelligence-based warning before the attack began. “If they wanted to maximize damage, they wouldn’t have allowed that much advanced warning time,” Inbar said, referring to Iran.

Another lesson is that Israel relies on other countries for optimal air defense.

“We learned that our system works and we learned that it works well with the American system,” said Uzi Rubin, a former head of Israel’s missile defense unit and one of the founders of Israel’s air defense programs. “It wasn’t just Israel, but also the United States and other allies, mainly, that helped defend Israel,” he said. In a sign of the close cooperation between the two countries, the head of U.S. Central Command, Gen. Michael Erik Kurilla, visited Israel this week and met with senior Israeli security officials. U.S. officials have also been working behind the scenes to avoid an all-out war with the Biden administration, which has been careful not to publicly criticize Israel’s operation in Tehran but to pressure all sides to de-escalate.

An Israeli reservist who handles air defense systems told the newspaper that he could not recall “such a level of defensive preparedness for a war in the north.” In recent days, the IDF has also rolled out a new alert system for the public to receive instructions in the event of a large-scale emergency.

While Israel’s air defense system is effective, it is not cheap. Kaliski previously estimated the cost of intercepting the Iranian missiles and drones on April 13 at 2.1 billion Israeli shekels, or more than $550 million, not including the costs incurred by the United States in shooting down the Iranian projectiles, which exceeded Israel’s costs by several times.