Origins under the Shah (1950s–1970s) 's research reactor.Iran's nuclear ambitions began under the rule of Shah
Mohammad Reza Pahlavi, with support from the United States and Western Europe. In 1957, Iran and the US signed a civil nuclear cooperation agreement as part of President
Dwight Eisenhower's "
Atoms for Peace" program. This led to the construction of Iran's first nuclear research facility at Tehran. In November 1967, the
Tehran Research Reactor (TRR) went critical – a 5 megawatt (thermal) light-water reactor, which initially ran on highly enriched uranium (HEU) fuel at 93% U-235, provided by the US, and was later converted in 1993 to use 20% enriched uranium with Argentine. Iran became one of the original signatories of the
NPT when it entered into force in March 1970, committing as a non-nuclear-weapon state not to pursue nuclear arms. By the mid-1970s, the Shah expanded Iran's nuclear energy ambitions. In 1974 he established the
Atomic Energy Organization of Iran (AEOI) and announced plans to produce 23,000 megawatts of electricity from a network of nuclear power plants over 20 years. Contracts were signed with Western firms: Iran paid over $1 billion for a 10% stake in the French
Eurodif consortium's uranium enrichment plant, and
West Germany's
Kraftwerk Union (Siemens) agreed to build two 1,200 MWe pressurized water reactors at
Bushehr. Construction of the
Bushehr Nuclear Power Plant began in 1975, and Iran also negotiated with France's Framatome to supply additional reactors. Plans were made for a full domestic nuclear fuel cycle, including uranium mining and fuel fabrication, with a new Nuclear Technology Center established at Isfahan. Further resolutions (1747 in 2007, 1803 in 2008, and 1929 in June 2010) broadened the sanctions to include arms embargoes, asset freezes on key individuals and entities, and restrictions on financial dealings. The final agreement is based upon "the rules-based nonproliferation regime created by the Nuclear Non-Proliferation Treaty (NPT) and including especially the
IAEA safeguards system". Enrichment was capped at 3.67% for 15 years, and the enriched uranium stockpile limited to 300 kg. Only 5,060 first-generation IR-1 centrifuges could operate at Natanz, and Fordow was repurposed for non-enrichment research. The Arak IR-40 reactor was to be redesigned and rebuilt, with its original core removed and filled with concrete to eliminate plutonium production capability. Iran agreed to provisionally implement the IAEA Additional Protocol, and accepted enhanced verification, including continuous surveillance of enrichment and conversion facilities, monitoring of uranium mines and mills, and oversight of centrifuge manufacturing. Iran's excess enriched uranium, including the bulk of its 20% material, was to be shipped abroad or down-blended. Over 13,000 centrifuges were dismantled. Limited R&D on advanced centrifuges was allowed under controlled conditions without accumulating enriched uranium. In exchange, the UN, US, and EU committed to stepwise sanctions relief: UN Security Council Resolution 2231 endorsed the JCPOA. It retained a conventional arms embargo for five years and ballistic missile restrictions for eight, and introduced a "snapback" mechanism allowing reimposition of sanctions in case of noncompliance. US and EU sanctions targeting Iran's energy, finance, shipping, and trade sectors were suspended. On "Implementation Day" (January 16, 2016), the IAEA verified Iranian compliance, leading to the unfreezing of billions in Iranian assets and restoration of access to international banking (e.g.,
SWIFT). Some US sanctions tied to terrorism and human rights remained in force.
United States withdrawal and Iranian violations (2018–2025) In 2018, the
Mossad reportedly stole nuclear secrets (a cache of documents from Iran's weaponization program) from a secure warehouse in the
Turquzabad district of Tehran. According to reports, the agents came in a truck semitrailer at midnight, cut into dozens of safes with "high intensity torches", and carted out "50,000 pages and 163 compact discs of memos, videos and plans" before leaving in time to make their escape when the guards came for the morning shift at 7 am. According to a US intelligence official, an "enormous" Iranian "dragnet operation" was unsuccessful in recovering the documents, which escaped through Azerbaijan. demonstrated that the AMAD Project aimed to develop nuclear weapons, that Iran had a nuclear program when it claimed to have "largely suspended it", and that there were two nuclear sites in Iran that had been hidden from inspectors. In 2018, the
United States withdrew from JCPOA, with President
Donald Trump stating that "the heart of the Iran deal was a giant fiction: that a murderous regime desired only a peaceful nuclear energy program". The US also contended that the agreement was inadequate because it did not impose limitations on Iran's ballistic missile program, and failed to curb its backing of proxy groups. In February 2019, the IAEA certified that Iran was still abiding by the international
Joint Comprehensive Plan of Action (JCPOA) of 2015. However, on 8 May 2019, Iran announced it would suspend implementation of some parts of the JCPOA, threatening further action in 60 days unless it received protection from US sanctions. In July 2019, the IAEA confirmed that Iran has breached both the 300 kg enriched uranium stockpile limit and the 3.67% refinement limit. On 5 November 2019, Iranian nuclear chief
Ali Akbar Salehi announced that Iran will enrich uranium to 5% at the
Fordow Fuel Enrichment Plant, adding the country had the capability to enrich uranium to 20% if needed. Also in November,
Behrouz Kamalvandi, spokesman for the Atomic Energy Organization of Iran, stated that Iran can enrich up to 60% if needed. President Hassan Rouhani declared that Iran's nuclear program would be "limitless" while the country launches the third phase of quitting from the 2015 nuclear deal. On January 3, 2020, the US assassinated Iranian
Quds Force commander
Qasem Soleimani, and Iran responded with missile strikes on US. bases. Two days later, Iran's government declared it would no longer observe any JCPOA limits on uranium enrichment capacity, levels, or stockpile size. In March 2020, the IAEA said that Iran had nearly tripled its stockpile of enriched uranium since early November 2019. In late June and early July 2020, there were several explosions in Iran, including one that damaged the Natanz enrichment plant (see
2020 Iran explosions). In September 2020, the IAEA reported that Iran had accumulated ten times as much enriched uranium as permitted by the JCPOA. On 27 November 2020, Iran's top nuclear scientist,
Mohsen Fakhrizadeh, was assassinated in Tehran. Fakhrizadeh was believed to be the primary force behind Iran's covert nuclear program for many decades. The
New York Times reported that Israel's Mossad was behind the attack and that
Mick Mulroy, the former Deputy Defense Secretary for the Middle East said the death of Fakhirizadeh was "a setback to Iran's nuclear program and he was also a senior officer in the
Islamic Revolutionary Guard Corps, and that "will magnify Iran's desire to respond by force." Throughout 2021 and 2022, Iran installed cascades of advanced centrifuges (IR-2m, IR-4, IR-6) at Natanz and Fordow, significantly increasing its enrichment output. In April 2021, a sabotage attack struck the Natanz enrichment plant, causing an electrical blackout and damaging centrifuges. Iran responded by further upping enrichment: days later, it began producing 60% enriched uranium, an unprecedented level for Iran, just short of weapons-grade (90% and above). This 60% enrichment took place at Natanz, and later at Fordow as well, yielding a stockpile that as of early 2023 exceeded ~70 kg of 60% uranium. On 25 June 2022, in a meeting with the senior diplomat of the EU,
Ali Shamkhani, Iran's top security officer, declared that Iran would continue to advance its nuclear program until the West modifies its "illegal behavior". In July 2022, according to an IAEA report seen by Reuters, Iran had increased its uranium enrichment through the use of sophisticated equipment at its underground Fordow plant in a configuration that can more quickly vary between enrichment levels. In September 2022, Germany, United Kingdom and France expressed doubts over Iran's sincerity in returning to the JCPOA after Tehran insisted that the IAEA close its probes into uranium traces at three undeclared Iranian sites. The IAEA said it could not guarantee the peaceful nature of Iran's nuclear program, stating there had been "no progress in resolving questions about the past presence of nuclear material at undeclared sites". United Nations Secretary-General
António Guterres urged Iran to hold "serious dialogue" about nuclear inspections and said IAEA's independence is "essential" in response to Iranian demands to end probes. In February 2023, the IAEA reported having found uranium in Iran enriched to 84%. The Iranian government has claimed that this is an "unintended fluctuation" in the enrichment levels, though the Iranians have been openly enriching uranium to 60% purity, a breach of the 2015 nuclear deal. In 2024, Iranian President
Masoud Pezeshkian expressed interest in reopening discussions with the United States on the nuclear deal. In late October 2024, during a series of
Israeli airstrikes in Iran carried out in response to a
ballistic missile attack earlier that month, Israel reportedly destroyed a top-secret nuclear weapons research facility known as the Taleghan 2 building, located within the
Parchin military complex. In November 2024, Iran announced that it would make new advanced centrifuges after IAEA condemned Iran's non-compliance and secrecy.
Current status and recent escalations (2025–present) In January 2025, the exiled opposition group NCRI alleged that Iran is developing
long-range missile technology under the
Islamic Revolutionary Guard Corps (IRGC), with some designs based on North Korean models. The NCRI said that these missiles, such as the
Ghaem-100 and
Simorgh, could carry nuclear warheads and reach targets as far as away, including parts of
Europe. These allegations have not been independently confirmed, but given that several past NCRI claims were later verified by inspectors, they warrant investigation. In March 2025, US President
Donald Trump sent a
letter to Ali Khamenei seeking to reopen negotiations. Ayatollah Ali Khamenei later said, "Some bullying governments insist on negotiations not to resolve issues but to impose their own expectations," which was seen as in response to the letter. In late March 2025, Khamenei's top advisor
Ali Larijani said Iran would have no choice but to develop nuclear weapons if attacked by the United States, Israel or its allies. In April 2025, Trump revealed that Iran had decided to undertake
talks with the United States for an agreement over its nuclear program. On 12 April, both countries held their first high-level meeting in Oman, followed by a second meeting on 19 April in Italy. On May 16, Trump sent Iran an offer and said they have to move quickly or else bad things would happen. On May 17, Khamenei condemned Trump, saying that he lied about wanting peace and that he was not worth responding to, calling the US demands "outrageous nonsense". Khamenei also reiterated that Israel is a "cancerous tumour" that must be uprooted. On May 31, 2025, IAEA reported that Iran had sharply increased its stockpile of uranium enriched to 60% purity, just below weapons-grade, reaching over 408 kilograms, a nearly 50% rise since February. The agency warned that this amount is enough for multiple nuclear weapons if further enriched. It also noted that Iran remains the only non-nuclear-weapon state to produce such material, calling the situation a "serious concern". On June 10, Trump stated that Iran was becoming "much more aggressive" in the negotiations. On 11 June, the Iranian regime threatened US bases in the Middle East, with Defense Minister
Aziz Nasirzadeh stating, "If a conflict is imposed on us... all US bases are within our reach, and we will boldly target them in host countries." The US embassy in Iraq evacuated all personnel. The Iran-backed Yemen-based
Houthi movement threatened to attack the United States if a strike on Iran were to occur.
CENTCOM presented a wide range of military options for an attack on Iran. UK issued threat advisory for ships on
Arabian Gulf. US Secretary of Defense
Pete Hegseth told Congress that Iran was attempting a nuclear breakout. On 12 June 2025, IAEA found Iran non-compliant with its nuclear obligations for the first time in 20 years. Iran retaliated by announcing it would launch a new enrichment site and install advanced centrifuges. In the early hours of June 13, Israel initiated
Operation Rising Lion, a large‑scale aerial assault targeting Iranian nuclear facilities, missile factories, military sites, and commanders across cities including Tehran and Natanz, marking the start of what would come to be known as the
Twelve-Day War of 13 to 24 June 2025. Iranian forces said they had shot down an Israeli drone. On 21 June, the US bombed the
Fordow Fuel Enrichment Plant, the
Natanz Nuclear Facility, and the
Isfahan Nuclear Technology/Research Center in an operation code named
Operation Midnight Hammer. In an address from the White House, Trump claimed responsibility for the destruction of the Fordow facility, stating "Iran's key nuclear enrichment facilities have been completely and totally obliterated." In early July 2025, Iran suspended co-operation with the United Nations'
International Atomic Energy Agency (IAEA). and all IAEA inspectors left Iran by July 4. In August 2025, Iran and European nations reached an agreement to recommence discussions focused on the complete restoration of Tehran's nuclear enrichment operations. France, Britain, and Germany have indicated that they may reinstate UN sanctions on Iran through a "quick return" mechanism should Tehran fail to engage in negotiations. On August 28, 2025, E3 members, France, Germany, and the United Kingdom, initiated the process of the snapback mechanism, with the prospect of freezing Iranian overseas assets, blocking arms deals with Iran, imposing penal action against development of Iran's ballistic missile program and further restricting Iran's military and nuclear activities. In a letter addressed to the president of the UN Security Council, the foreign ministers of the E3 stated that since 2019, Iran had "increasingly and deliberately ceased performing its JCPOA commitments", including "the accumulation of a highly enriched uranium stockpile which lacks any credible civilian justification and is unprecedented for a state without a nuclear weapons program". The letter detailed additional Iranian violations of the agreement despite the fact that the E3 "have consistently upheld their agreements under the terms of the JCPOA". The activation opened a 30-day window, intended to reengage Iran, "whose refusal to cooperate with the International Atomic Energy Agency's (IAEA) inspectors started the crisis", in diplomatic negotiations before full restoration of sanctions. According to Euronews, Iran's Foreign Minister Abbas Araghchi declared that it was "unjustified, illegal, and lacking any legal basis" and promised that "The Islamic Republic of Iran will respond appropriately". On 28 September, UN sanctions were officially reimposed on Iran. In October 2025, former defence minister and current political adviser to the Supreme Leader,
Ali Shamkhani, stated "If I returned to the defence portfolio, I would move toward building an atomic bomb", and declared that if he could return to the 1990s, "we would definitely build the atomic bomb". On 3 March 2026, the
International Atomic Energy Agency (IAEA) confirmed that while
recent bombings had failed to destroy the Natanz nuclear facility, the significant damage which had been done to its entrance buildings had now made it inaccessible. The report stated that although such warheads would require uranium enriched to 90%, this could be achieved in a matter of weeks if Iran were to process its existing stockpile of 441 kg of 60% uranium with its advanced IR-4 and IR-6 centrifuges; However, according to a US official, the methods Iran had been exploring at the time could produce a nuclear weapon, though not one which could be delivered by a ballistic missile. == Main facilities ==