Iran has been fortifying underground "cities" for decades to house one of the largest and most diverse ballistic missile arsenals in the Middle East.
Many of Iran's missile sites are located in and around the capital, Tehran.
There are at least five known underground "missile cities" in various provinces across Iran, including Kermanshah, Semnan, and near the Gulf region.
According to a 2023 report by the US-based Foundation for Defense of Democracies, Iran was continuing to develop underground missile depots complete with transport and firing systems, and subterranean missile production and storage centres.
Ben Zala, a senior lecturer in politics and international relations at Monash University, said Iran had made protecting its missile stockpiles a priority.
"They know that the missile program is a target, that's why they've put such an emphasis on underground facilities," he told the ABC.
"They have fortified those structures which makes them really hard to completely destroy."
The US has warned of the increasing "lethality and precision" of Iranian missiles, insisting nuclear talks also included restrictions on its weapons program.
But Tehran views its missile force as a strategic priority to deter threats from the US, Israel and their allies, and to exert regional power.
Iranian officials have drawn a line in the sand — its ballistic missiles program will "never" be up for negotiation.
What are ballistic missiles?
Ballistic missiles are a rocket-propelled weapon fit with either nuclear or conventional warheads.
Launched like a bullet from a gun, it follows an unpowered, free-falling trajectory toward targets.
When hitting its highest speed the missile becomes ballistic, soaring to high altitudes before taking a deep and fast dive.
The pace and steep angle generally make the weapons more difficult to intercept than cruise missiles and drones.
Shahram Akbarzadeh, a professor of Middle East and Central Asian politics at Deakin University, said decades of sanctions had considerably limited Iran's ability to maintain and modernise its armed forces.
But it had managed to grow and maintain its drone and missile program which was now the "last strategic asset in its arsenal".
"Iran used to have a network of proxies under the umbrella of 'axis of resistance' — and groups such as Hezbollah and Hamas were supposed to protect Iran from attacks by Israel and the United States," Professor Akbarzadeh told the ABC.
"But in more than two years of war Israel has seriously depleted these forces.
"Without missiles Iran will have very limited opportunities to respond to future attacks — which could be imminent."
What types of missiles does Iran have?
According to US intelligence estimates Iran has 14 different types of ballistic missile.
Before the country was targeted in US and Israeli strikes last year it had an inventory of about 3,000.
"Iran continues to bolster the lethality and precision of its domestically produced missile and UAV [unmanned aerial vehicle] systems, and it has the largest stockpiles of these systems in the region," the US Office of the Director of National Intelligence said in March 2025.
The arsenal includes close-range, short-range, and medium-range systems.
The longest-range variant can travel up to 2,000 kilometres.
The semi-official Iranian news agency ISNA published a graphic in 2024 showing nine types of Iranian missiles it said could reach Israel.
Reaching Israel from Iran requires missiles with ranges of more than 1,000km.
Iran has reportedly used a variety of medium-range ballistic missiles in past attacks, including the Emad and Ghadr-1, and Iran's first hypersonic Fattah-1.
In June 2023, Iran presented what officials described as its first domestically made hypersonic ballistic missile, the IRNA news agency reported.
Hypersonic missiles can fly at least five times faster than the speed of sound and on a complex trajectory, which makes it difficult to intercept.
Professor Akbarzadeh said Iran was known to showcase some of its latest missiles to send a message to Israel and the US, but the size and capabilities of the arsenal was "sometimes inflated by the authorities".
Missiles used in regional attacks
Iran's missile capabilities were on display during the 12-day war with Israel in June last year.
Iran fired about 500 ballistic missiles at Israel during that time, with some attacks involving waves of more than 100.
Some of the missiles penetrated Israel's multi-layered air defence systems.
"Estimates vary, but it looks like the Iron Dome system intercepted about a third or so of the ballistic missiles that Iran fired over the last year," Professor Zala said.
"So if you are in Iran's position you definitely want to keep that ballistic missile program if possible."
Israeli authorities said 28 people were killed and more than 3,000 injured in the Iranian strikes.
Iran said Israel's attacks during the 12-day conflict killed 935 people in the country.
Tehran also responded to US participation in the war by firing missiles at the US Al Udeid air base in Qatar.
Tehran gave advance warning of the attack and no injuries were reported.
Attempts to limit missiles 'idealistic'
The US has been threatening further military action against Tehran if deals were not reached on its nuclear and ballistic missile programs.
Ahead of talks with Iran last week US Secretary of State Marco Rubio said negotiations needed to include "the range of their ballistic missiles".
But missiles were not on the agenda.
After the meeting Iranian Foreign Minister Abbas Araghchi reiterated that the "missile issue" and other defence matters were "in no way negotiable, neither now nor at any time in the future".
Professor Zala said it was very unlikely Iran would agree to any ballistic missile restrictions.
"It's quite an idealistic, I would say even a naive aim for the Americans to even think they could get Iran to come to the table on some sort of ballistic missile limitation deal," Professor Zala told the ABC.
"Iran's under no international obligation to do so. There is no precedent for a state accepting limits on its missile program simply because another state wants them to."
And with the latest meeting between Israeli Prime Minister Benjamin Netanyahu and US President Donald Trump on the Tehran talks yielding "nothing definitive", the issue was unlikely to disappear.
Mr Netanyahu has referred to Iran's "attempt to build atomic weapons" and "20,000 ballistic missiles" as "two lumps of cancer".
"The prime minister believes that all negotiations must include limiting the ballistic missiles, and ending support for the Iranian axis," Mr Netanyahu's office said in a statement.
ABC/Reuters
