Part I of the Iran Series

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FOREIGN PERSPECTIVE // March 2026 // by Simon

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The news labeled the bombing of Tehrean on February 28, 2026, as a turning point. But anyone who had followed Iran’s nuclear story for the past decade felt different. It felt like an arrival. The end of a road that started years ago. It started on May 8, 2018, when Donald Trump walked away from the Iran nuclear deal.

To understand how we got here, you need to know about one diplomatic tool. Most people have never heard of it. It is called the snapback mechanism.

A Safety Net Built Into the Deal

The snapback was part of the 2015 Iran nuclear deal, known as the JCPOA. It was written into UN Security Council Resolution 2231. It gave any country in the deal the power to bring back all UN sanctions against Iran automatically. No vote needed. No veto is possible from Russia or China.

The idea was simple. Sanctions relief would only stay in place if the Security Council agreed to keep it. If Iran broke the deal, one country could pull the whole thing back. Azadeh Zamirirad from the German Institute for International and Security Affairs (SWP) referred to it as the most effective tool for penalizing breaches of arms control agreements. It served as the insurance policy outlined in the agreement.

On August 28, 2025, France, Germany, and the UK used it. Iran had enriched uranium to 60 percent purity. It had blocked UN inspectors. Its uranium stockpile was 25 times the JCPOA limit. On September 27, 2025, sanctions came back into force. The tool worked exactly as designed.

Did it Change Anything?

That depends on what you were hoping for.

If the goal was to show that Europe could still act without the United States, then yes. The Europeans proved that multilateral institutions can still have teeth.

But if the goal was to change Iran’s behavior, then no. Tehran threatened to leave the Nuclear Non-Proliferation Treaty. It kept blocking inspectors. It kept building up its nuclear program. Zamirirad had seen this coming. Iran, she argued, would weigh every nuclear concession against what it cost its own security. The snapback raised the pressure. It did not change the calculation.

The Real Break Happened in 2018

The snapback debate was always about symptoms. The real cause goes back further.

In May 2018, Trump pulled the United States out of the JCPOA. Seyed Hossein Mousavian wrote about it in Foreign Affairs right after it happened. Trump’s decision sent a clear message to Iranian leaders. Talking to Washington is pointless. That debate inside Tehran was now over.

Iran’s response was gradual but clear. In May 2019, Tehran started walking back its JCPOA commitments step by step. It always pointed to the US withdrawal as the reason. Richard Nephew wrote in Foreign Affairs that by 2025, Iran had stockpiled enough enriched uranium for several nuclear warheads. Its breakout time had fallen from over a year to just days

Here is the core problem. The snapback was triggered because Iran broke the deal. But Iran broke the deal because the United States had already left it. The tool was solid. Years earlier, the foundation it rested on had crumbled.

What the Snapback could not Fix

Zamirirad’s analysis of Trump’s second term makes this plain. Maximum pressure did not work. It hurt Iran’s economy. It did not produce any meaningful concessions on nuclear or regional issues. What it did produce was a Tehran that turned east. A Tehran that leaned on Russia and China. Tehran viewed its nuclear program as the sole surviving asset following the collapse of its regional network in 2024.

The snapback was a genuine effort by the Europeans. But it could not undo seven years of broken trust. It could not reverse Iran’s nuclear advances. It arrived too late.

A Final word

The snapback deserves respect. It was real multilateral diplomacy. It worked procedurally under serious political pressure. But it could not replace the one thing that makes arms control agreements last: political commitment from all sides.

When Washington left the JCPOA in 2018, it did more than abandon a deal. It proved right everyone in Tehran who had argued that diplomacy with the US leads nowhere. Iran’s nuclear program accelerated. A chain of events began that no snapback could stop.

The war that started on February 28, 2026, has many causes. But the deepest one goes back eight years. To a decision made in Washington. Whose consequences we are still living with today

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Sources

SWP – Stiftung Wissenschaft und Politik

• Zamirirad, Azadeh: Neue Atomgespräche mit Iran. Herausforderungen und Handlungsoptionen für europäische Politik. SWP-Aktuell 22/2025, Berlin, Mai 2025.
• Zamirirad, Azadeh: In unruhigem Fahrwasser – was Trumps zweite Amtszeit für Iran bedeutet. In: Trumps Rückkehr und Europas außenpolitische Herausforderungen. SWP-Studie 2025/S 03, S. 43–47.
• Zamirirad, Azadeh: Iran und die Neuordnung des Nahen Ostens. Zeitschrift für Außen- und Sicherheitspolitik 18 (2025), S. 1–11.
• Meier, Oliver / Zamirirad, Azadeh: What Europe can do now to save the nuclear deal with Iran. SWP Point of View, 10. Mai 2019.
• Zamirirad, Azadeh: Irans Blick nach Osten. Asien, Eurasien und die ordnungspolitische Vision der Islamischen Republik. SWP-Studie 25/2020

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