The Iran Nuclear Deal was an agreement reached between the United States, Iran, the United Kingdom, France, Germany, Russia, and China. It strictly limited the amount of enriched uranium and enrichment equipment Iran could have for a period of 15 years. In exchange, sanctions on Iran were to be lifted, and Iranian funds frozen after the 1979 revolution were to be returned.

Trump described the Obama administration’s “embarrassing” treaty with Iran to be “decaying and rotten.” He withdrew the United States from the deal unilaterally in 2018 and restored prior sanctions. The European Union sought to maintain the agreement, and passed a blocking statute to ban all EU citizens and business with complying with US sanctions on Iran. Iran continued to take part in the agreement until January of 2020, when a US drone strike killed a senior Iranian official.

Before becoming President, Trump said multiple times that Obama would provoke Iran into conflict to secure re-election.

BBC News – Iran nuclear deal: Trump pulls US out in break with Europe allies
The New York Times – Trump Abandons Iran Nuclear Deal He Long Scorned
Business Insider – Here’s what’s in the 2015 nuclear deal with Iran that the country withdrew from amid heightened tensions with the US
Reuters – EU aims to block U.S. sanctions on Iran
Wikipedia – Joint Comprehensive Plan of Action