Context

• Talks to revive the 2015 nuclear deal between Iran and world powers are set to resume, as representatives from Iran and the United States return to Vienna for a new round of discussions mediated by the European Union.

What was the 2015 Iran nuclear deal?

• The deal, formally known as Joint Comprehensive Plan of Action (JCPOA), is a landmark accord signed between Iran and a coalition of world powers including the US, the UK, China, Russia, France, and Germany (collectively known as P5+1).
• The relatively moderate regime of President Hassan Rouhani agreed to dismantle much of Iran’s nuclear programme, and open its facilities to greater international monitoring. In return, the world powers agreed to lift many of the sanctions imposed on the country, opening its economy to billions of dollars of lost revenue.
• In essence, the agreement focused on eliminating Iran’s stockpiles of enriched uranium and plutonium (needed to produce a nuclear weapon), and on limiting the number and type of centrifuges Iran could operate.
• Iran’s economy, after suffering years of recessions, currency depreciation, and inflation, stabilised significantly after the deal took effect, and its exports skyrocketed.
• Israel, America’s closest ally in the Middle East, strongly rejected the deal, and other countries like Iran’s great regional rival Saudi Arabia, complained that they were not involved in the negotiations even though Iran’s nuclear programme posed security risks for every country in the region.
• Critics also point out that since 2015, Iran has increased its support for regional proxies, and the Islamic Revolutionary Guard Corps (IRGC), which the US has designated a terrorist organisation, has expanded its activities.
• However, backers of the deal believe that it succeeded in its main objective, which was to contain Iran’s nuclear capabilities.

What happened after the US pulled out of the deal?

• In 2020, under Trump’s presidency, the US announced its intention to abandon the deal and reinstate sanctions. However, the other partners objected to the move, stating that since the US was no longer part of the deal, it could not unilaterally reimpose sanctions.
• The other powers, in an attempt to keep the deal alive, launched a barter system known as INSTEX to facilitate transactions with Iran outside the US banking system. 
• Despite the efforts of the US’s allies, the deal was essentially dead — and Tehran accused the US of reneging on its commitments, and blamed Europe for capitulating to US unilateralism.
• After Trump abandoned the deal and reinstated sanctions, Iran ramped up its nuclear programme in earnest, returning to approximately 97 per cent of its pre-2015 nuclear capabilities.
• Still, the new US sanctions hit the Iranian economy hard, leading to a wave of protests across the country.

Reference

https://www.aljazeera.com/news/2022/8/3/iran-nuclear-talks-to-restart-in-vienna-with-eu-mediation