From the Shah's American-supplied reactors to a collapsed deal and an active standoff — here is how one of the world's most consequential diplomatic crises actually developed.
Few foreign policy issues generate more heat and less light than Iran's nuclear program. The coverage tends to oscillate between alarm and dismissal, rarely pausing to explain how we got here. This piece attempts to fix that.
Understanding the Iran nuclear file requires going back further than most people expect — not to 2003, not to the Islamic Revolution, but to the 1950s, when the United States actively helped Iran build its first nuclear infrastructure.
In 1957, under President Eisenhower's "Atoms for Peace" program, the United States signed a nuclear cooperation agreement with Iran — then ruled by Shah Mohammad Reza Pahlavi, a close American ally. Washington provided Iran with a research reactor, enriched uranium, and technical training.
By 1967, the Tehran Nuclear Research Centre was operational. By the mid-1970s, the Shah had announced ambitions to build twenty nuclear power plants across Iran. Western companies, including American, German, and French firms, were lining up for contracts. There was no international alarm. Iran was on the right side of the Cold War, and nuclear energy was the future.
Then came 1979.
The Islamic Revolution that toppled the Shah in 1979 upended every assumption Washington had made about Iran. Most of the foreign nuclear contractors pulled out. Construction on the Bushehr reactor was abandoned. For most of the 1980s, Iran's nuclear program stalled.
But the program did not die. And the war with Iraq — in which Saddam Hussein used chemical weapons against Iranian troops with minimal international condemnation — left a deep institutional memory in Tehran about the consequences of being militarily vulnerable.
After the Iran-Iraq War ended in 1988, Iran quietly resumed nuclear development. With help from Pakistan's A.Q. Khan network, Iran acquired centrifuge designs capable of enriching uranium to weapons-grade levels. Construction began on facilities at Natanz and Arak that Iran did not declare to international inspectors.
Then, in August 2002, an Iranian opposition group revealed the existence of the Natanz enrichment facility and the Arak heavy water reactor. The world now knew Iran had been operating a covert nuclear infrastructure for years.
What followed was two decades of on-again, off-again diplomacy punctuated by escalating sanctions. The most significant breakthrough came in 2015 with the Joint Comprehensive Plan of Action. Tehran agreed to cap its uranium enrichment at 3.67 percent, reduce its stockpile by 98 percent, and submit to intrusive IAEA inspections. In exchange, crippling economic sanctions were lifted.
By 2018, the IAEA had conducted more inspections of Iranian nuclear facilities than of any other country on earth. All reports confirmed Iranian compliance with the JCPOA's terms.
In May 2018, President Trump withdrew the United States from the JCPOA. Iran initially stayed in the deal, hoping European signatories would find a way to sustain economic benefits without the U.S. They couldn't.
By 2019, Iran began systematically breaching the JCPOA's limits. Enrichment levels climbed — first to 20 percent, then to 60 percent, then to 83.7 percent. Weapons-grade is 90 percent.
As of 2026, Iran's nuclear program is more advanced than at any point in its history. The breakout time — how long it would take Iran to produce enough weapons-grade uranium for a bomb — has shrunk from roughly twelve months in 2015 to what analysts now estimate is a matter of weeks.
How we got here: a program that America helped build, a revolution that made it threatening, a secret expansion, a historic deal that was abandoned, and a decade of escalation that has left all parties worse off than when they started.
