Backgrounder: Timeline of Iran-U.S. tensions since 2015

U.S. President Donald Trump said Saturday that “Iran can never have a nuclear weapon” as he confirmed the launch of "major combat operations" against the country.

For its part, Iranian officials have reiterated their long-standing position that the country is not seeking nuclear weapons, a pledge that formed the basis of the Joint Comprehensive Plan of Action (JCPOA), from which Trump unilaterally withdrew the United States during his first term.

Tensions between Iran and the U.S. have shaped the Middle East for decades, revolving around Iran's nuclear program, regional influence and recurring diplomatic crises.

After years of sanctions, covert operations and periodic negotiations since 1979, the 2015 JCPOA represented a rare opportunity for de-escalation and rapprochement.

The following timeline traces key events from that moment through early 2026, highlighting the ebb and flow of diplomacy, sanctions, military confrontations and domestic unrest that have defined U.S.-Iran relations.

July 2015 

The JCPOA was signed, with Iran accepting significant limits on its nuclear program in exchange for sanctions relief, primarily from the United States and the European Union. The deal was endorsed by the UN Security Council and supported by Russia and China. It was widely regarded as the closest Iran and Western powers had come to diplomatic rapprochement since 1979.

May 2018 

During his first term, President Donald Trump unilaterally withdrew the U.S. from the JCPOA and mounted a "maximum pressure" campaign, reinstating and expanding sweeping sanctions. It sent Iran's economy into a sharp and severe decline.

January 2020

On January 3, the U.S. assassinated Qassem Soleimani, commander of Iran's Islamic Revolutionary Guard Corps (IRGC) Quds Force, in a drone strike at Baghdad International Airport. Iran retaliated on January 8, launching ballistic missiles at U.S. military bases in Iraq.

The Biden administration (January 2021- January 2025) 

The Biden administration sought to revive the nuclear deal, but talks became protracted and ultimately reached an impasse, while Iran continued to advance its nuclear program, maintaining it was for "peaceful purposes."

February 2025 

After returning to the White House, President Trump swiftly reinstated his "maximum pressure" strategy, signing new executive orders targeting Iran. He warned that any attempt by Iran to assassinate him would result in the country's destruction.

June 13-24, 2025

Israel and Iran engaged in a direct military confrontation in what became known as the Twelve-Day War, also referred to as the Iran–Israel War, with the U.S. providing significant defensive support to Israel.

June 22, 2025

U.S. military forces joined Israeli strikes on three Iranian nuclear facilities at Fordow, Natanz and Isfahan. This marked the first time since 1979 that the U.S. had directly attacked major facilities inside Iran, signaling Washington's formal entry into the Israel-Iran conflict.

June 23-24, 2025

Iran launched retaliatory missile strikes on the U.S. military's Al Udeid Air Base in Qatar, which resulted in no casualties. A ceasefire between Israel and Iran brokered by Qatar brought the Twelve-Day War to an end on June 24.

January 2026

Tensions spiraled through a cycle of U.S. military threats, sanctions and support for protests inside Iran. Iran responded by demonstrating military readiness, engaging in diplomatic outreach and signaling openness to negotiations. Both sides engaged in brinkmanship over Iran's nuclear program and regional stability.

February 2026

The U.S. and Iran held three rounds of indirect talks mediated by Omani Foreign Minister Sayyid Badr bin Hamad bin Hamood Albusaidi. No agreement was reached.

Read more:

Backgrounder: Three rounds of indirect Iran-U.S. nuclear talks