US President Donald Trump has announced American bombers have attacked Iran's heavily fortified Fordow nuclear facility, as well as two other nuclear sites in Iran.
"The US military carried out massive precision strikes on the three key nuclear facilities in the Iranian regime: Fordow, Natanz, and Isfahan," he said in a televised address from the White House.
"I can report to the world the strikes were a spectacular military success.
"Iran's key nuclear enrichment facilities have been completely and totally obliterated."
Earlier, on Truth Social, the president said a "full payload of bombs" was dropped on the primary site of the attacks, the Fordow Fuel Enrichment Plant.
The once-secret uranium facility was built deep underground near the city of Qom.
This satellite image, captured before the US said it struck the facility, shows the plant nestled in a mountain.
It is accessed via tunnels, evidenced by entrances visible from the surface.
The bulk of the nuclear facility is located under an estimated 90 metres of rock.
At its heart is a large hall that houses centrifuges to enrich uranium to certain percentages.
There are thought to be blast or debris traps near its entrances as additional defences against air strikes.
The existence of the facility became public knowledge in 2009, when then-US president Barack Obama stood alongside the leaders of France and the UK and revealed Iran had been building a "covert uranium enrichment facility near Qom for several years".
He said a week earlier, Tehran had written to the UN's nuclear watchdog, the International Atomic Energy Agency (IAEA), mentioning "a new enrichment facility, years after they had started its construction".
IAEA inspectors were allowed into the facility in late 2009, where they were shown two halls, according to a 2019 report by the Institute for Science and International Security (ISIS).
The think tank is led by David Albright, a leading American physicist and nuclear weapons expert, who is also a former weapons inspector.
The report said one hall contained what one might expect for the enrichment of uranium for use in nuclear reactors, but the other hall was being stripped and modified at the time.
"These observations contributed to several inspectors, including ones who were experts in gas centrifuges, becoming suspicious that this hall was for the onward enrichment of uranium up to weapon-grade," the report, authored by Mr Albright and two others, read.
"Of course, Iran denied any such work," it said.
Under the 2015 Joint Comprehensive Plan of Action (JCPOA), colloquially known as the Iran deal, Fordow was allowed to operate as a nuclear physics and technology centre, but was banned from uranium enrichment and storing nuclear material at the site for 15 years.
"The US and allied negotiators were not able to convince Iran to shut down this site, even though it has no credible civilian nuclear justification," the ISIS report said.
'Atomic Archive' revealed further details
More information about Fordow came to light from documents seized by Israel's foreign intelligence service, Mossad, in a 2018 raid on a Tehran warehouse.
The raid on Iran's "Atomic Archive", as it was labelled by Israel, has been extensively documented by the New York Times and Washington Post.
The agents torched their way into some of the 32 safes contained in the warehouse, after a two-year surveillance operation, stealing and smuggling out of the country tens of thousands of documents and compact discs containing memos, videos, and plans relating to Iran's past nuclear research.
Israeli Prime Minister Benjamin Netanyahu announced the heist in April 2018 — presenting some of the documents in a televised address, arguing against the Iran deal.
Later, select media outlets were given access to some of the haul by Israeli officials, who decided what they could and could not see.
At the time, Iran said the documents were fraudulent.
"Iran has always been clear that creating indiscriminate weapons of mass destruction is against what we stand for as a country, and the notion that Iran would abandon any kind of sensitive information in some random warehouse in Tehran is laughably absurd," a statement from its UN mission in New York read.
But among the haul was a picture showing support facilities for the Fordow nuclear facility, then named the Al Ghadir project site.
It also contained designs and diagrams for the underground portion of the project, according to the Institute for Science and International Security.
The ABC's 3D map of the facility, featured above, is based on these blueprints — which are understood to be the only publicly available layouts of the facility.
The IAEA says Iran stopped implementing all of the commitments it made as part of the Iran deal in February 2021 — including allowing daily access to Fordow, on request, for monitoring.
The watchdog was still able to verify what was happening at Fordow at less regular intervals.
Its latest report, released more than a week ago, said the facility was enriching uranium to 60 per cent — adding changes in its enrichment process had "significantly" increased the rate of production.
A low percentage of enrichment — about 3 to 5 per cent — is required for the uranium to be used in civilian settings, like a nuclear power plant.
A high level — generally about 90 per cent — is needed for use in modern atomic weapons.
"It's actually easier to go from an enrichment of 60 per cent to 90 per cent than it is to get to that initial 60 per cent," said nuclear physicist Kaitlin Cook in The Conversation.
"It's a fairly trivial last step to go 90 per cent, which is why people were alarmed," said Jeffrey Lewis, an expert in nuclear non-proliferation from the Middlebury Institute of International Studies.
Iran has long denied having a nuclear weapons program.
"Iran declared … quite a few times that … it does not have any nuclear, you know, just program in terms of military aspects," the Iranian ambassador to Australia, Ahmad Sadeghi, told the ABC's David Speers on Wednesday.
The 'bunker buster'
Fordow's location means conventional bombs, like those in Israel's possession, would have had little to no effect on the parts of the facility buried deep.
According to experts from the Royal United Services Institute (RUSI), there was only one conventional weapon thought to be big enough to reach and destroy Fordow: the GBU-57 Massive Ordnance Penetrator (MOP), sometimes called the "bunker buster".
It weighs more than 13 tonnes, stands six metres tall and is specifically designed to "defeat hard and deeply buried targets" like bunkers and tunnels, according to a fact sheet from a US Department of Defense agency.
It is said to be able to reach depths of up to 60 metres before exploding.
"Multiple GBU-57/B impacts would almost certainly be required to reach the Fordow Fuel Enrichment Plant, with the second bomb impacting inside the hole made by the first," said Justin Bronk, an air power specialist at RUSI.
The United States is the only country known to have this kind of bomb — and the only one with the aircraft approved to deliver it, the B-2 Spirit Stealth Bomber.
The US has not confirmed what kind of bombs were used in its attacks on Iran's nuclear sites, but US officials told Reuters that B-2 bombers were used.
B-2 bombers operate out of a US Air Force base in Missouri.
On Saturday, local time, air traffic communication monitors reported two flight groups of US B-2 bombers heading west over the Pacific, likely to a US air base in Guam, a US island territory in the Pacific.
It is unclear if these particular bombers were involved in the attacks.
In April, the uniquely shaped aircraft were seen at an air base on the island of Diego Garcia, in the Indian Ocean.
That same month, US media reported the B-2s were being stationed there in a display of power to countries like Iran.
Inside Iran, there has been confirmation of the strikes, but the extent of the damage at the Fordow, Natanz, and Isfahan sites could not be independently verified.
Iranian state news agency, Mehr, has reported that the Fordow and Natanz facilities had sustained "limited damage".
Iranian state media quoted Behrouz Kamalvandi, spokesman for the Atomic Energy Organization of Iran (AEOI), saying critical equipment and materials had been relocated from the Fordow site before the bombing, minimising the impact.
Omar Rahman, from the Middle East Council on Global Affairs, told the ABC that Iran was very likely to strike back at the US.
"Iran has its back to the wall for the moment, and it needs to retaliate to show some sort of credibility for the regime," he said.
"I think you're going to see some sort of military response here against US assets and military installations in the region.
"That could be against aircraft carriers in the Persian Gulf, it could be against any number of the bases, and tens of thousands of US soldiers stationed in the region."
Speaking from the White House after the attacks, Mr Trump thanked and congratulated Israeli Prime Minister Benjamin Netanyahu, saying the pair had "worked as a team like perhaps no team has ever worked before".
"Iran, the bully of the Middle East, must now make peace," Mr Trump said.
"If they do not, future attacks will be far greater and a lot easier.
"Remember, there are many targets left.
"Tonight's was the most difficult of them all by far.
"There's no military in the world that could have done what we did tonight — not even close."
Notes about data used in this story:
The satellite image used in the 3D model is from Planet Labs. Elevation data is from the Shuttle Radar Topography Mission (SRTM) and map boundaries are from Natural Earth.
