Iran’s missile strike on Diego Garcia: What it means for Europe

On 21 March 2026, Iran launched two ballistic missiles toward the US-UK military airbase on Diego Garcia, located in the Indian Ocean, marking the longest-range strike attempt attributed to Tehran to date. According to initial reporting, one missile failed in flight while the other was intercepted by a US interceptor launched from a naval asset operating in the region before reaching its target. 

While the attack itself caused no damage, the range of the ballistic missile strike caught international observers off guard. Until then, Iran was known to operate several types of medium-range ballistic missiles with ranges of up to 2,000 kilometres. A strike against a military base located 3,800 kilometres away therefore implies a significant increase in missile range compared to previously known systems. 

But Iran’s ability to deploy longer-range systems should not have come as a surprise. For decades, Iran has been developing ballistic missiles, many of which have seen extensive operational use since 2024. Given this background and expertise, extending the range of Iran’s ballistic missile systems, potentially up to 4,000 kilometres, represents more of an evolution than a revolution. 

It remains unclear which type of ballistic missile Iran used in the strike, though there are two main possibilities. The first is a two-stage ballistic missile, which employs an additional booster stage to extend range beyond what a single-stage system can achieve. Iran’s civilian space-launch vehicle programme, widely regarded by analysts and intelligence agencies as a cover for developing longer-range ballistic missiles, has produced several systems that could form the basis for such a capability. 

The second is the use of a modified single-stage ballistic missile. Because ballistic missile range is highly sensitive to payload weight, reducing the warhead size can significantly extend the missile’s range. Some Iranian systems, such as the Khorramshahr medium-range ballistic missiles – officially able to fly 2,000 kilometres – carry comparatively large warheads exceeding 1,500 kilograms. By reducing that payload to just a few hundred kilograms, it may be possible to extend the missile’s range sufficiently to reach the British island. 

Whatever missile Iran used in the attack, the strike demonstrates that the distance at which it can hold targets at risk has increased. This also implies a potential ability to strike into the heart of Europe. That said, European governments should not overreact to these developments. 

Europe, together with the United States, has for years been preparing for an Iranian ballistic missile threat directed at the continent. This is a key reason why the US operates the Aegis Ashore ballistic missile defence system in Poland and Romania, equipped with land-based SM-3 interceptors, capable of engaging Iranian medium- and intermediate-range ballistic missiles. 

European navies, alongside US maritime assets in the region, also deploy relevant interceptor technologies in the Mediterranean, including French-Italian-made Aster 30B1 and Aster 30B1NT interceptors. Germany has recently declared initial operational capability for the Arrow missile defence system, imported from and combat-proven in Israel, which has demonstrated high levels of effectiveness against Iranian ballistic missiles. Europe is therefore far from defenceless against such a threat. 

At the same time, Iranian ballistic missiles have underwhelmed international observers, particularly in terms of accuracy. Iranian medium-range ballistic missiles appear unable to effectively hold even relatively large area targets, such as airbases or major infrastructure facilities. In practice, they appear effective only as a terror weapon, employed indiscriminately against population centres. 

Unless Iranian engineers can significantly improve ballistic missile accuracy – which appears unlikely – the expected precision of an intermediate-range ballistic missile reaching deep into Europe would be even lower. As a result, the military threat posed by these systems is very limited and arguably negligible, although they could still be used to threaten larger European cities.

Regardless of the technical characteristics of Iranian missiles or European interceptor capabilities, it should also be recalled that an attack on a European NATO state would trigger Article 5 of the Alliance’s collective defence clause. An attack against one member constitutes an attack against all, and Iran would have to fear a response from the entire Alliance. It is highly unlikely that Iran would accept such risks in the near to medium-term. 

That said, recent developments in the Middle East, particularly where they relate to Iran’s ballistic missile programme, demonstrate that Europe must remain vigilant and cannot afford to fall behind. An anticipatory foreign policy that seeks to identify and prepare for emerging threats, combined with continued investment in missile defence and Europe’s own deep-strike capabilities, is necessary to ensure the continent’s security in a turbulent geopolitical environment. 

Fabian Hoffmann is a doctoral research fellow at the Oslo Nuclear Project at the University of Oslo and a non-resident fellow at the Center for European Policy Analysis.