On 20 March the Wall Street Journalreported that Iran had launched two ballistic missiles towards the shared United Kingdom–United States military airbase on the Indian Ocean island of Diego Garcia, citing ‘multiple US officials’. The report was later confirmed by the British government, but denied by Iran, which characterized it as a ‘false flag’ operation. However, little further information has come to light about the incident.
If the reports are accurate, this would mean that Iran has demonstrated the capability to launch missiles with a range of nearly 4000 kilometres from its borders. To date, Iran has claimed to adhere to a self-imposed missile range moratorium of 2000 km.
In this Q&A, SIPRI Associate Senior Researcher Dr Markus Schiller, an expert on rockets and missiles, explains what we can glean from the limited information available about the missile technologies that might have been involved and about Iran’s long-range strike capabilities.
Q: If Iran did launch missiles that reached close to Diego Garcia, would this change what we know about Iran’s missiles?
MS: Not really. While the late supreme leader Ayatollah Ali Khamenei stated many years ago that he had imposed a limit of 2000 km on Iran’s ballistic missile range, it was clear to observers that Iran was working on technologies and missiles that would allow Iran to quickly cross that threshold.
One example is the Khorramshahr missile, which was first tested about 10 years ago. Iran stated that this liquid-fuelled, single-stage ballistic missile only had a range of 2000 km, while also claiming that it could carry payloads of up to 1800 kilograms. It stands to reason that the Khorramshahr could have a much longer range with a lighter warhead. Also, Iran has introduced technologies in recent years under its purported space programme, for example the large solid rocket motors tested with the Zuljanah rocket since 2021, that suggested it could eventually increase the range of its missiles.
Q: What missiles could Iran have launched against Diego Garcia?
MS: We do not have much to go on, but the obvious candidate is the Khorramshahr missile, which would be capable of covering the 3800 km or so to Diego Garcia, if only just, carrying a very light warhead, and using some of its propellant reserves for extra range.
However, in a statement the day after the attack, Israeli Chief of General Staff General Eyal Zamir added the detail that Iran had launched ‘a two-stage intercontinental ballistic missile’ at Diego Garcia. While parts of the statement might be lost in translation, this would likely rule out the single-stage Khorramshahr.
There are several possibilities for an Iranian two-stage missile with this range, for example derivatives of one of Iran’s ‘space launchers’. However, it is possible that the statement reflected the fact that the Khorramshahr separates its warhead in flight, so US forces would have seen two objects approaching the base.
Q: What are the implications for the USA and its allies if missiles did indeed reach near to Diego Garcia from Iran?
MS: When it comes to military implications, not much. One missile reportedly failed in flight while the other was shot down, suggesting that they are prone to problems and also that they can be dealt with by active air-defence systems. Also, the Diego Garcia base is a strip of atoll 1 km across at its widest point. Hitting such a small target with ballistic missiles like the Khorramshahr has proved difficult in the past, especially at such a distance. These are not advanced intercontinental ballistic missiles (ICBMs) with complex post-boost vehicles. Also, a direct hit from the kind of very light warhead that the Khorramshahr could carry such a distance would damage a building with a direct hit, but would not have much effect if, for example, it hit an airfield.
However, the idea that Iran can send a ballistic missile 4000 km has more of a symbolic value, sending a clear message that Iran could target European capitals as far away as London. But we have known for years that this was the case, and it is hard to see what Iran could hope to gain from doing so. While such a strike could inflict some damage, it is more likely that it would fail or at least miss its intended target. In this regard it is worth noting that efforts are already underway in Europe to defend against exactly this kind of missile threat—for example, Germany’s procurement of the Israeli Arrow-3 missile-defence system. And as Iran’s leaders must be aware, such a strike against Europe would almost certainly trigger a reaction that puts the Iranian regime in a worse situation than it is in already. This regime is not stupid, and it certainly knows very well how and when to play its cards.
ABOUT THE AUTHOR(S)
Dr Markus Schiller is an Associate Senior Researcher in the SIPRI Armament and Disarmament Research Programme and the CEO of Munich-based consulting company ST Analytics.
On 20 March the Wall Street Journal reported that Iran had launched two ballistic missiles towards the shared United Kingdom–United States military airbase on the Indian Ocean island of Diego Garcia, citing ‘multiple US officials’. The report was later confirmed by the British government, but denied by Iran, which characterized it as a ‘false flag’ operation. However, little further information has come to light about the incident.
If the reports are accurate, this would mean that Iran has demonstrated the capability to launch missiles with a range of nearly 4000 kilometres from its borders. To date, Iran has claimed to adhere to a self-imposed missile range moratorium of 2000 km.
In this Q&A, SIPRI Associate Senior Researcher Dr Markus Schiller, an expert on rockets and missiles, explains what we can glean from the limited information available about the missile technologies that might have been involved and about Iran’s long-range strike capabilities.
Q: If Iran did launch missiles that reached close to Diego Garcia, would this change what we know about Iran’s missiles?
MS: Not really. While the late supreme leader Ayatollah Ali Khamenei stated many years ago that he had imposed a limit of 2000 km on Iran’s ballistic missile range, it was clear to observers that Iran was working on technologies and missiles that would allow Iran to quickly cross that threshold.
One example is the Khorramshahr missile, which was first tested about 10 years ago. Iran stated that this liquid-fuelled, single-stage ballistic missile only had a range of 2000 km, while also claiming that it could carry payloads of up to 1800 kilograms. It stands to reason that the Khorramshahr could have a much longer range with a lighter warhead. Also, Iran has introduced technologies in recent years under its purported space programme, for example the large solid rocket motors tested with the Zuljanah rocket since 2021, that suggested it could eventually increase the range of its missiles.
Q: What missiles could Iran have launched against Diego Garcia?
MS: We do not have much to go on, but the obvious candidate is the Khorramshahr missile, which would be capable of covering the 3800 km or so to Diego Garcia, if only just, carrying a very light warhead, and using some of its propellant reserves for extra range.
However, in a statement the day after the attack, Israeli Chief of General Staff General Eyal Zamir added the detail that Iran had launched ‘a two-stage intercontinental ballistic missile’ at Diego Garcia. While parts of the statement might be lost in translation, this would likely rule out the single-stage Khorramshahr.
There are several possibilities for an Iranian two-stage missile with this range, for example derivatives of one of Iran’s ‘space launchers’. However, it is possible that the statement reflected the fact that the Khorramshahr separates its warhead in flight, so US forces would have seen two objects approaching the base.
Q: What are the implications for the USA and its allies if missiles did indeed reach near to Diego Garcia from Iran?
MS: When it comes to military implications, not much. One missile reportedly failed in flight while the other was shot down, suggesting that they are prone to problems and also that they can be dealt with by active air-defence systems. Also, the Diego Garcia base is a strip of atoll 1 km across at its widest point. Hitting such a small target with ballistic missiles like the Khorramshahr has proved difficult in the past, especially at such a distance. These are not advanced intercontinental ballistic missiles (ICBMs) with complex post-boost vehicles. Also, a direct hit from the kind of very light warhead that the Khorramshahr could carry such a distance would damage a building with a direct hit, but would not have much effect if, for example, it hit an airfield.
However, the idea that Iran can send a ballistic missile 4000 km has more of a symbolic value, sending a clear message that Iran could target European capitals as far away as London. But we have known for years that this was the case, and it is hard to see what Iran could hope to gain from doing so. While such a strike could inflict some damage, it is more likely that it would fail or at least miss its intended target. In this regard it is worth noting that efforts are already underway in Europe to defend against exactly this kind of missile threat—for example, Germany’s procurement of the Israeli Arrow-3 missile-defence system. And as Iran’s leaders must be aware, such a strike against Europe would almost certainly trigger a reaction that puts the Iranian regime in a worse situation than it is in already. This regime is not stupid, and it certainly knows very well how and when to play its cards.
ABOUT THE AUTHOR(S)