Iran has been seeking to bolster its air defences as the military prepares for the possibility of an Israeli or US strike against Tehran’s nuclear infrastructure if negotiations over its enrichment programme break down.
Many of Iran’s most-advanced surface-to-air missiles and radars — including its long-range Russian-made S-300 systems — were destroyed or damaged by Israeli air strikes in October and April 2024.
This, coupled with successful Israeli strikes on Iranian proxies such as Lebanese militants Hizbollah and Yemen’s Houthi rebels, has led to the perception that Iran is at its most vulnerable to air attack in decades.
However, experts say many elements of Iran’s air defences remain intact or appear to have been repaired in recent months.
Western intelligence assessments and satellite imagery reviewed by defence analysts suggest that Iran has since repositioned several surface-to-air missile launchers, including S-300 systems, near key nuclear sites such as Natanz and Fordow.
Some kit has also been shown in public in recent months, with a parade of weaponry — including an S-300 launcher and a radar truck — displayed in Tehran at “Army Day” celebrations last month.
An S-300 unit was also shown launching a surface-to-air missile during military exercises in February using a new, Iranian-designed radar — possibly because its original radar was inoperable, according to Nicole Grajewski of the Carnegie Endowment in Washington.
“Iran definitely wants to negate the narrative that its advanced air defences are destroyed,” she said.
Mohammad Bagheri, the chief of staff of Iran’s armed forces, this month touted Iran’s preparedness for an attack.
“We are witnessing a remarkable improvement in the capability and readiness of the country’s air defence,” he said, trumpeting a “several-fold increase in investments”.
“The enemies of the Iranian nation must understand that any violation of our country’s airspace will inflict significant damage upon them,” he said.
Though negotiations with Washington over the future of Iran’s nuclear programme are ongoing, US President Donald Trump — who abandoned an earlier nuclear deal with Iran during his first term — has threatened to attack the Islamic republic if talks break down.
Washington has demanded that Iran stop enriching uranium, something it says is necessary to prevent the country acquiring nuclear weapons, while Tehran insists it must be able to continue enriching for civilian use.
The US in April ordered six B-2 bombers — the largest deployment of the aircraft ever — to Diego Garcia, the Indian Ocean base which is expected to be the likely launch point for any strikes against Iran.
Israel, which has already shown it can hit Iranian air defences, has been pushing the US to support strikes against Iran. Experts have said there is a risk that Israel would attack without Washington’s consent if it felt Trump agreed to a weak deal.
During its strikes last year, Israel targeted radar and missile sites with ballistic missiles launched from well outside the S-300’s maximum range of 200km. Boosters for these missiles, made by Israel’s Rafael Corporation, were found in the Iraqi desert hundreds of kilometres away.
The effectiveness of these attacks is still hotly debated.
Open source satellite images show a few direct hits, such as on an S-300 radar truck at an air base near Isfahan after the April 2024 strike. But imagery after the October strikes showed many S-300 sites empty, making it unclear whether the missiles had been destroyed or simply moved.
“There is not much hard evidence,” said Sam Lair, a research associate at the James Martin Center for Nonproliferation Studies.
However, Iran was clearly bruised. Western intelligence assesses that Tehran believes its air defences “underperformed” last year and has taken steps such as repositioning and diversifying launchers and radars, according to two people familiar with these reports.
Lair and two co-authors this month published an analysis of a snippet from an Iranian propaganda video that inadvertently revealed the inside of an air defence command centre. A detailed analysis by Lair and a colleague suggested the defences were “fragmented in nature”.
But an attack on Iran’s nuclear sites, located in hardened underground bunkers — the facility at Natanz is built into a mountain — would be far more complicated than anything Israel attempted last year.
Were the US to be involved, the B-2 bombers based in Diego Garcia would likely drop heavy 30,000lb GBU-57 bunker buster bombs directly on the target, according to research published in March by the Royal United Services Academy in London.
If it acted alone, Israel — which lacks heavy bombers or a way to deliver such large ordnance — would have more limited options.
They would likely use F-35 stealth fighters, armed with 2,000lb BLU-109 precision bombs, or F-15 fighter bombers carrying 4,000lb GBU-28 bombs, either of which would require multiple hits on the same crater to punch through hardened shelters, RUSI said.
This might require many sorties, possibly using mid-air refuelling tankers that themselves might be vulnerable to long-range surface-to-air missiles or drones. Since last summer, Israel has struck targets in Yemen at least nine times at a distance similar to a strike on Iran.
They would also be well within range of the still-operational array of short and medium surface-to-air missiles, and loitering anti-aircraft drones, with which Iran has layered its air defences. It would be hard to know how many of these had been destroyed before a concerted bombing campaign started.
As well as short-range systems such as the Russian Tor-M1, Iran’s arsenal also includes locally developed surface-to-air missiles like the long-range Bavar-373 and the medium-range Khordad-15. These homegrown weapon programmes grew out of frustration with Russia’s slow deliveries and refusal to sell more advanced systems like the S-400, according to Fabian Hinz, a research fellow at the UK-based International Institute for Strategic Studies.
“From the Iranian side this effort attempts to replicate the success story of Iran’s ballistic missile development programme,” he said.
Jon Alterman, chair of global security and geostrategy at the Washington-based Center for Strategic and International Studies, said navigating such defences would not be straightforward for Israel. “But is that beyond Israeli capabilities? No, of course not. The Israelis have been training for precisely this scenario for decades.”
So has Iran. Suppressing Iran’s air defences before bombing the nuclear sites would be an hours- or even days-long battle, pitting aircrews against surface weapons operators, using fighters and cruise missiles supported by electronic jamming aircraft and anti-radiation missiles to destroy radar.
“Israel has established near air dominance over Iran,” said Robert Tollast, a researcher at UK think-tank RUSI. “But a strike like this would require waves and waves of aircraft over several hours. Crew fatigue enters the picture. The longer they are over Iran, the more likely that something goes wrong.”
Iranian radar, vulnerable to radiation-seeking missiles and having to switch off to survive, could be blinded by Israeli jamming, he said. However, even if most of Iran’s high-end air defences are subdued or destroyed, there are systems that could get lucky.
“You have a very intense air battle, with a significant chance that an Israeli pilot would be paraded on Iranian TV.”
Even Iran’s less advanced missiles could be successful. For example, Syria in 2018 downed an Israeli F-16 with a S-200 surface-to-air missile, a Russian system that came into service in the late 1960s. The plane crashed in northern Israel and both pilots survived.
Yuri Lyamin, an air defence specialist and one of the world’s top experts on Russian air defence systems at Moscow’s Centre for Analysis of Strategies and Technologies, said the success of an attack would not be preordained.
“While everyone pays attention to the S-300, Iran attaches great importance to the creation of the most mobile, modern air defence systems which can quickly change positions, hide in shelters, making them less vulnerable to stand off strikes with long-range missiles,” he said.
The outcome “would depend on how well attackers work together, versus how well the defending force can work together. The best team will win”.
Additional reporting by Bita Ghaffari in Tehran
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