Ten years of nuclear paper
Published 4 October 2026
The Iranian nuclear program began with an American present. In November 1967 the five-megawatt Tehran Research Reactor, supplied by the United States, went critical. According to the Arms Control Association's timeline it ran on uranium enriched to about 93 percent, which the United States also supplied. It was converted to 20 percent fuel in 1993. In February 1970 Iran's parliament ratified the Nuclear Non-Proliferation Treaty.
The dispute proper started in August 2002, when the political wing of the Mujahideen-e Khalq, an opposition group the Arms Control Association describes as a terrorist organization, held a press conference declaring that Iran had built nuclear facilities near Natanz and Arak. Inspectors followed. On 4 February 2006 a special meeting of the International Atomic Energy Agency's board referred Iran to the UN Security Council and called on it to suspend enrichment-related activities. On 11 April 2006 Iran said it had enriched uranium for the first time, to about 3.5 percent, at the Natanz pilot plant. That is reactor-fuel grade, and the argument ever since has been about the distance from there to something else.
Stuxnet, Fordow and a deal in Vienna
The next decade mixed sabotage with centrifuges. On 16 September 2010 a security expert identified the Stuxnet computer virus as a directed attack against an Iranian nuclear-related facility, likely the Natanz enrichment plant. By November 2012 the IAEA reported that Iran had installed the roughly 2,800 centrifuges that its Fordow plant was designed to hold, and was still producing 20 percent uranium. Britannica's timeline notes that after Hassan Rouhani's election in 2013, Barack Obama called him, the most direct contact between the two countries' leaders since 1979.
The diplomacy moved in steps. An interim Joint Plan of Action took effect on 20 January 2014: Iran halted enrichment to 20 percent, started blending down half its stockpile of 20 percent uranium, and stopped work on the Arak reactor, according to the IAEA's compliance report. A framework followed on 2 April 2015, and on Tuesday, 14 July 2015 Iran and the P5+1 announced the comprehensive deal. The UN Security Council endorsed it unanimously on 20 July. Britannica summarizes the trade: in exchange for easing some sanctions, Iran agreed to dismantle a nuclear reactor, limit uranium enrichment for at least 15 years, and accept monitoring of its compliance. The deal formally began on 18 October 2015, and on Saturday, 16 January 2016 the IAEA verified that Iran had met its commitments, which triggered the lifting of sanctions.
It is worth recording how fussy the early compliance was, because the file's later chapters are about numbers that are not fussy at all. In February 2016 the IAEA reported that Iran held 130.9 metric tons of heavy water, slightly above the 130-ton limit, and that Iran had shipped 20 tons out. In November 2016 the figure was 130.1 tons, over the cap again, and Iran announced plans to transfer the excess. By 6 December the IAEA verified that 11 tons had been shipped and that Iran was back under the limit. A heavy-water overage of one-tenth of a ton, reported, explained and fixed within weeks, is what a functioning inspection regime looks like. Remember it.
The exit
The agreement was never universally loved. Britannica notes that it faced resistance from members of Congress of both parties who argued it left Iran too much power in the region. In March 2016 the then-candidate Donald Trump told an audience at AIPAC that his number one priority was to dismantle the deal, and after his election he called it the worst deal ever negotiated. In 2018 he withdrew the United States from it, citing what he described as its defects, and reimposed sanctions. The BBC reported that since 2019 Iran has increasingly breached the restrictions of the deal in retaliation, particularly those on enriched-uranium production.
Europe held on. The three European parties, France, Germany and the United Kingdom, say they triggered the deal's dispute-resolution mechanism in January 2020 and spent months in 2020 and 2021 on talks to restore it. They say Iran rejected two offers from the deal's coordinator in 2022 and kept expanding its program. Those are European claims in a European statement, and they are the E3's own account of its record. The BBC's framing of the other side of the story is that Iran's breaches since 2019 came in retaliation for the American exit.
The June 2025 vote
The last peacetime milestone came on Thursday, 12 June 2025, the day before Israel attacked. The IAEA's board of governors formally declared Iran in breach of its non-proliferation obligations, which the BBC said was the first such finding in 20 years. Nineteen of the 35 board members voted yes. Russia, China and Burkina Faso voted no, eleven abstained and two did not vote. The resolution cited Iran's "many failures" to give full answers about undeclared nuclear material and activities and said the agency could not verify that there had been no diversion of nuclear material.
The week before, an agency report had said Iran held enough uranium enriched to 60 percent, near weapons grade, to make potentially nine nuclear bombs, according to the same BBC report. Iran insisted that its activities were entirely peaceful and that it would never seek nuclear weapons. It called the board's resolution political and said it would open a new enrichment facility. The text, the BBC added, noted that the matter now raised questions within the competence of the UN Security Council, which could snap back the sanctions lifted in 2015 if Iran failed to fulfil its obligations. The E3 had said that could happen later in the year.
The next morning the question stopped being diplomatic.
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