Then-President Barack Obama lauded the deal – officially known as the Joint Comprehensive Plan of Action (JCPOA) – as a “chapter in this pursuit of a safer and more helpful and more hopeful world,” and later called it “the strongest non-proliferation agreement ever negotiated.”

Iranian President Hassan Rouhani, at the same time, called the landmark agreement a “historic deal and Iranians will be proud of it for generations to come.” People in Tehran danced in the streets to celebrate.

Four-and-a-half years later, this cooperation between the US and Iran has relapsed into enmity, and the optimism has faded into tensions so high they risk all-out war.

President Donald Trump withdrew the US from the deal in May 2018, citing a lack of trust in Iran and calling Obama’s work a bad deal. He then imposed punitive sanctions to cripple Iran’s economy in an unsuccessful effort to force the regime’s leaders to comply with US demands on its behavior.

Trump’s actions have been widely viewed as the catalyst of a series of escalating tensions between the US and Iran, which bubbled to a historic height in recent days.

On January 3, the US killed revered Iranian military leader Qassem Soleimani in a drone strike ordered by Trump.

Two days later, Iran announced it was fully withdrawing from the JCPOA, having since last summer openly taken incremental steps from its commitments that could allow it to develop a potential nuclear weapon.

On Thursday, Rouhani said the country was enriching more uranium than it did before completing the JCPOA in 2015.

Trump called time on Iran’s growing military confrontation by killing its beloved General Qasem Soleimani.

The Europeans are calling time on Tehran’s diplomatic escalation — namely its intentional drift from compliance with the nuclear deal, or the Joint Comprehensive Plan of Action (JCPOA), as it is formally known — by triggering the accord’s dispute resolution mechanism, known as paragraph 36.

Paragraph 36 sets a short timeline to escalate (and hopefully resolve) a dispute. First it goes to the deal’s Joint Commission body then, if consensus can’t be reached, on to the signatories’ foreign ministers, before eventually reaching the UN Security Council. Iran is on notice they must come back to compliance.

France, Germany and the UK triggered this Tuesday while Tehran was reeling from the loss of Soleimani and grappling with the international and domestic fallout from downing Ukraine International Airlines flight 752, with the loss of 176 lives. The backlash includes significant street protests calling for the overthrow of the Supreme Leader.

There is a short window before Iran regains its composure and its usually intransigent posture, or at least that seems to be the European calculation: Strike while the iron is hot.