What Happened After the U.S. Left the Iran Deal. Part II of ONM’s Iran Nuclear Series
Giovanni Losito
Part I: The Five Myths Americans Were Told About the Iran Nuclear Deal
Part II: What Happened After the U.S. Left the Iran Deal
Part III: How Close Is Iran to a Nuclear Weapon — and What the Science Actually Says
When the United States withdrew from the 2015 Iran nuclear agreement—formally known as the Joint Comprehensive Plan of Action (JCPOA)—the move was framed as a strategy to force Iran back to the negotiating table for a tougher deal.
That isn’t how events unfolded.
Instead, the years that followed saw the slow collapse of the agreement’s restrictions and a steady expansion of Iran’s nuclear program.
To understand what happened next, you have to start with the moment the deal unraveled.
The Day the Deal Collapsed
May 8, 2018
President Donald Trump announced the United States would withdraw from the nuclear agreement and reimpose sweeping economic sanctions on Iran.
In remarks from the White House, Trump described the deal as:
“A horrible, one-sided deal that should have never, ever been made.”
The administration launched what it called a “maximum pressure” campaign, designed to cut off Iran’s oil revenue and isolate its financial system from global markets.
Supporters of the decision argued the agreement failed to address Iran’s ballistic missile program and its support for armed groups across the Middle East.
Critics responded that the deal had a narrower purpose: preventing Iran from developing a nuclear weapon.
Both arguments had merit.
But the nuclear limits only worked as long as the deal existed.
Once the United States walked away, the guardrails holding the program in place began to fall away as well.
What the Deal Actually Did
Before the U.S. withdrawal, the JCPOA imposed strict technical limits on Iran’s nuclear program.
Among them:
Uranium enrichment capped at 3.67 percent
Uranium stockpile limited to 300 kilograms
Thousands of centrifuges dismantled
Continuous monitoring by the International Atomic Energy Agency
These restrictions were not theoretical.
For years after the agreement took effect, inspectors from the International Atomic Energy Agency repeatedly verified that Iran was complying with the deal.
The limits dramatically extended Iran’s estimated “breakout time”—the time required to produce enough weapons-grade material for a nuclear weapon.
Under the agreement, that timeline was estimated at roughly one year.
The First Year After Withdrawal
After the United States left the agreement, Iran did not immediately abandon its commitments.
For roughly twelve months, Tehran continued observing most of the deal’s limits while European governments attempted to salvage the arrangement.
But American sanctions hit hard.
Oil exports collapsed.
Foreign investment dried up.
The economic relief promised under the agreement never fully materialized.
By May 2019, Iran began stepping away from the restrictions.
The Escalation Timeline
What followed was not a sudden nuclear breakout.
It was something slower—and in many ways more dangerous.
A steady, incremental dismantling of the deal’s limits.
May 2019
Iran suspends several commitments under the deal.
July 2019
Iran exceeds the 300-kilogram uranium stockpile limit and begins enriching above 3.67 percent.
November 2019
Iran resumes enrichment at the Fordow underground facility, which the agreement had previously converted into a research site.
2020–2022
Iran installs advanced centrifuges capable of enriching uranium far more quickly than the older machines allowed under the deal.
By the mid-2020s
Iran begins enriching uranium to 60 percent purity.
For context, civilian nuclear reactors typically use uranium enriched to 3–5 percent.
Weapons-grade uranium is generally enriched to around 90 percent.
Once enrichment reaches 60 percent, nuclear experts say most of the difficult technical work has already been done.
How Close Did Iran Get?
Reports from the International Atomic Energy Agency indicate Iran has accumulated hundreds of kilograms of uranium enriched to 60 percent purity.
That material would still require additional enrichment before it could be used in a weapon.
Iran maintains its nuclear program is peaceful.
Western intelligence agencies remain skeptical.
What most analysts agree on, however, is that Iran’s nuclear capabilities expanded significantly after the agreement collapsed.
The Credibility Problem
The collapse of the deal also created a new challenge for diplomacy.
Iranian negotiators began pointing to the U.S. withdrawal as evidence that any future agreement could simply be reversed by the next administration.
That concern was not limited to Tehran.
European diplomats involved in the negotiations warned that the abrupt reversal reinforced the perception that American policy had become volatile—shifting sharply between administrations and sometimes driven by sudden political decisions rather than long-term strategy.
Critics of the withdrawal described the approach as “maximum pressure with minimal predictability.”
Supporters argued unpredictability could strengthen negotiating leverage.
Either way, convincing Iran that a future deal would survive long enough to matter became far more difficult.
The “Obliterated” Claim vs. Reality
Another claim that circulated during the confrontation with Iran was that the country’s nuclear infrastructure had been “obliterated.”
The reality is more complicated.
Iran’s nuclear program is spread across multiple facilities, including enrichment plants, research centers, underground installations, and a network of trained scientists.
Facilities can be damaged.
Equipment can be destroyed.
But nuclear knowledge cannot be erased.
Over the years sabotage operations and covert actions have slowed Iran’s program at times. But inspectors and nuclear experts consistently note that the country has rebuilt or replaced damaged components.
Today, Iran’s enrichment capabilities are more advanced than they were when the nuclear deal was first signed in 2015.
That does not mean Iran possesses a nuclear weapon.
But it does mean the program the JCPOA once boxed in has grown significantly since the agreement collapsed.
Calling Balls and Strikes
Supporters of leaving the deal raised legitimate concerns.
The agreement did not restrict Iran’s missile program.
It did not stop Tehran’s regional proxy activity.
And some provisions were designed to expire over time.
Those criticisms were real.
But the central promise made when the United States withdrew—that economic pressure would force Iran into accepting a stronger replacement agreement—never materialized.
Instead, the restrictions unraveled.
And Iran’s enrichment program expanded.
A Wider Warning from Nuclear Scientists
The broader nuclear risk environment has also grown more dangerous.
On January 27, 2026, the Bulletin of the Atomic Scientists announced that its symbolic Doomsday Clock had been moved to 85 seconds before midnight, the closest point to global catastrophe in the clock’s history.
The organization cited a combination of threats—geopolitical conflict, weakening arms-control agreements, emerging technologies, and nuclear proliferation risks.
Iran’s nuclear program is not the only factor driving those concerns. But the collapse of one of the world’s most significant nuclear agreements inevitably feeds into the broader anxiety about where global nuclear policy is headed.
The clock is not a scientific measurement. It is a warning.
And right now, the scientists who maintain it believe the world is moving in the wrong direction.
Where Things Stand Now
Today the nuclear standoff sits in an uneasy gray zone.
Iran insists it is not pursuing nuclear weapons.
The United States, Israel, and many European governments remain deeply skeptical.
International inspectors warn that reduced monitoring makes it harder to verify what is happening inside Iran’s nuclear program.
Diplomatic talks continue on and off in places like Vienna and Oman, but the trust that once supported the original agreement has been badly damaged.
The result is a reality few policymakers predicted in 2018.
The nuclear program the agreement once boxed in is now larger, more advanced, and closer to weapons-grade capability than it was when the deal was still in force.
Next in the Series
Part III
How Close Is Iran to a Nuclear Weapon — and What the Science Actually Says