“Iran fired two ballistic missiles on March 20, 2026, at the Indian Ocean island of Diego Garcia, which hosts a strategically important joint U.S.-U.K. military base, according to U.S., U.K. and Israeli officials.”

“One missile broke apart during flight, and the other appears to have been destroyed by U.S. missile defenses.”

“Iran has denied responsibility for the launches.”

“Diego Garcia is about 2,500 miles (4,000 kilometers) from Iran, which is about twice as far as the top range Iran has declared that its ballistic missiles have.”

“However, there’s no evidence that Iran has developed a new type of missile or that it can otherwise hit targets at the longer range.”

“Iran most likely modified an existing type of missile, but increasing a missile’s range poses significant challenges.”

“Short-range ballistic missiles can fly about 300 to 600 miles (500 to 1,000 km) and can be launched from mobile trucks.”

“Medium-range ballistic missiles have ranges of about 600 to 1,800 miles (1,000 to 3,000 km).”

“Intermediate-range ballistic missiles operate over about 1,800 to 3,400 miles (3,000 to 5,500 km), putting much larger geographical regions at risk.”

“Intercontinental ballistic missiles, or ICBMs, have a range of about 3,100 to 6,200 miles (5,000 to 10,000 km).”

“The ranges of these missiles – up to 500 miles (800 km) – are insufficient for Iran to use them against Israel directly because the closest distance between the two countries is about 550 miles (900 km).”

“Maintaining control of the missile and hitting a target with sufficient accuracy becomes increasingly more difficult as range is extended.”

“The simplest modification to extend a missile’s range is to reduce its payload.”

“In the Iranian attack on Diego Garcia, however, one of the missiles failed in flight and the other appeared to have been destroyed by U.S. defenses.”

“Having successfully launched satellites into space using two-stage rockets, however, perhaps it is not too surprising that Iran has been able to build on those successes to achieve longer ranges for its missiles.”

“The December 2025 attack with hundreds of missiles being shot down is another claim.”

“Scaling up from short range to medium range to intermediate requires larger and larger rockets, which presents a number of increasingly difficult technical challenges.”

“Iran has reportedly demonstrated this with the Khorramshahr, using a smaller warhead that gives it a range of 1,800 miles (3,000 km).”

“Iran has an extensive ballistic missile program. The country has been developing a number of short-range ballistic missiles for many years.”

“ICBMs also have a small payload mass, and this in part explains why militaries more often load them with nuclear warheads than conventional chemical explosives.”

“The missile failure may indicate that Iran is attempting to operate these systems at distances they are not reliably capable of.”

“Iran has also developed intermediate-range ballistic missiles such as the Shahab-3, Sejjil and Khorramshahr weapons. These missiles have ranges of up to 1,250 miles (2,000 km), which means they can reach Israel directly from Iran.”

“The apparent ability of the U.S. to defend against the second missile suggestsத that Iran's intermediate-range missiles may be vulnerable to U.S. defenses.”

“The size of the rocket also determines how much payload the missile can deliver.”