More than forty years after the 1979 Iranian Revolution, relations between the United States and Iran remain tense. As Iran advances its nuclear program and trains proxy forces throughout the Middle East, the potential for violent conflict persists.
Iran has pursued a nuclear program since at least 1957, with varying degrees of success. By the late 1980s during a brutal war with Iraq, Iran decided to develop nuclear weapons to ensure its security, and, consequently, Iran pursued agreements with China and Russia throughout the 1990s to support its ongoing research into the development of nuclear weapons. Under growing scrutiny and international pressure, in 2003-04 Iran agreed to terminate its nuclear weapons program, insisting only that it maintain its nuclear centrifuges for nuclear energy. However, the International Atomic Energy Agency (IAEA) discovered and exposed that Iran had continued to pursue nuclear weapons later in 2003, and a coalition of countries known as the P5+1—the United States, China, France, Germany, Russia, and the United Kingdom—began a series of negotiations in an effort to constrain Iran’s nuclear program and prevent the development of nuclear weapons. To encourage Iran to cease uranium enrichment and come to the negotiating table, the UN Security Council imposed economic sanctions [PDF] on Iran in 2006. The sanctions resulted in 20 percent domestic unemployment [PDF] and a severe contraction of Iran’s gross domestic product, which in part enabled Hassan Rouhani to win Iran’s presidential election in 2013—he campaigned on promises to lift sanctions and restore the economy.
Over the next two years, the United States convened several rounds of bilateral talks and led the P5+1 in negotiations with Iran, which resulted in the adoption of the Joint Comprehensive Plan of Action (JCPOA) in 2015. Once key parties had signed the agreement, the UN Security Council approved resolution 2231, which paved the way for sanctions relief. The JCPOA requires Iran to reduce its stockpile of enriched uranium by 98 percent for fifteen years, cut the number of operating centrifuges by two-thirds for ten years, and provide International Atomic Energy Agency (IAEA) inspectors access to enrichment facilities within twenty-four days if the IAEA suspects violations. Moreover, if the IAEA confirms violations, the JCPOA allows for the immediate reinstatement of sanctions. After the JCPOA entered into force on January 16, 2016, Iran received sanctions relief that totaled nearly $100 billion.
Though the JCPOA limited Iran’s nuclear ambitions, its regional ambitions continued to grow. Iran has continued to arm and train Shiite militants through its Quds Force—the Islamic Revolutionary Guard Corps’ (IRGC) international arm—which has exacerbated sectarian divisions in the Middle East. The Quds Force has provided advanced armed drones to Hezbollah in Lebanon, trained and funded more than one hundred thousand Shiite fighters in Syria, supplied ballistic missiles and drones to Yemen’s Houthis, and helped Shiite militias in Iraq build missile capabilities. The U.S. government considers Iran to be the foremost state sponsor of terrorism—spending more than one billion dollars on terrorist financing annually—and there are between 140,000 and 185,000 IRGC-Quds Force partner forces in Afghanistan, Gaza, Lebanon, Pakistan, Syria, and Yemen.
Iran has also continued to develop ballistic missiles, which, according to the United States, violates UN resolution 2231. In response, the United States continues to impose sanctions on Iran’s ballistic missile program and the IRGC through the Countering Iran’s Destabilizing Activities Act of 2017 and the Countering America’s Adversaries Through Sanctions Act.
Because the JCPOA only addressed Iran’s nuclear program—and not its revisionism or ballistic missile programs—the Donald J. Trump administration asserted that the agreement was a stopgap. Thus, in May 2018, President Trump withdrew the United States from the JCPOA, pledging to seek a more comprehensive deal. Secretary of State Mike Pompeo subsequently issued twelve requirements for a new agreement, which Iranian Supreme Leader Ali Khamenei responded to by proposing seven conditions for remaining in the JCPOA. Starting in May 2018, the Trump administration reimposed sanctions and issued new ones against Iran and demanded that European countries withdraw from the JCPOA as part of a new containment strategy. France, Germany, and the United Kingdom refused to do so and attempted to devise a backchannel for trade with Iran; the Trump administration responded by threatening European allies and European companies with consequences should they continue to do business with Iran. Iran’s oil exports have since decreased by more than half. U.S. sanctions sparked the worst economic crisis Iran has faced in forty years and emboldened Iranian hardliners.
While the Trump administration pursued a strategy of maximum pressure to bring Iran to the negotiating table, Iran began to contravene the JCPOA’s restrictions on its nuclear program, raising tensions. In April 2019, the United States designated the IRGC a terrorist organization—the first time the United States classified part of another government as such. In May 2019, after intelligence suggested Iran and its militias were preparing to attack U.S. troops in Iraq and Syria, the United States deployed B-52 nuclear-capable bombers, an aircraft carrier strike group, and additional Patriot missile batteries to the Middle East to deter Iran. Over the next month, six oil tankers in or near the Strait of Hormuz were attacked, which U.S. government officials blamed on Iran, and the United States deployed an additional 2,500 troops to the Middle East.
In late June 2019, Iran downed a U.S. Global Hawk drone in the Strait of Hormuz, and President Trump approved—and quickly canceled—a retaliatory strike, instead ordering a cyberattack and imposing new sanctions. On July 1, 2019, Iran exceeded the JCPOA’s cap on uranium stockpiles. Later in July, the United States downed an Iranian drone in the Strait of Hormuz after the drone approached a U.S. Navy ship.
In September 2019, the United States deployed a small number of troops to bolster Saudi air defenses after a Houthi strike on a Saudi oil facility that Saudi Arabia blamed on Iran. On December 31, Trump blamed Iran for backing protests that tried to seize the U.S. Embassy in Baghdad. Days later, on January 3, 2020, tensions peaked when the United States killed Qasem Soleimani, the commander of Iran’s Quds Force, in a Baghdad air strike. In response, Iran said it would no longer adhere to restrictions under the nuclear deal, and it accidentally shot down a Ukrainian passenger plane while on high alert. In late 2020, Trump continued to ratchet up sanctions and Iran boosted uranium enrichment to levels well beyond the limits of the nuclear deal after one of its top nuclear scientists, Mohsen Fakhrizadeh, was killed.
A worsening conflict with Iran would have significant economic, political, and security implications for the United States. Should the United States and Iran engage in military conflict, Iran could attempt to block the Strait of Hormuz, through which 30 percent of the world’s oil flows, which would raise oil prices globally. Moreover, the United States risks isolating itself from already beleaguered allies: in June 2019, NATO refused to commit to working with the United States to secure freedom of navigation in the Strait of Hormuz. A U.S.-Iran confrontation could trigger an escalation of proxy warfare in countries like Syria and Yemen or an increase in Iranian missile strikes targeting the seventy thousand U.S. troops in the Middle East.
Tensions between Iran and the United States have eased under the President Joe Biden administration. Biden appointed Robert Malley as the new U.S. special envoy to Iran, and in April 2021, the two countries began talks in Vienna on returning to compliance with the nuclear deal. However, neither side wanted to be the first to resume its obligations under the deal. Shortly after, Iran blamed Israel for an explosion at its Natanz nuclear facility and subsequently boosted uranium enrichment to 60 percent, closer to the level required for a bomb. In June, talks stalled after Ebrahim Raisi won the Iranian presidential election and took a more hardline stance toward negotiations. In early 2022, Israel cast the Negev Forum, which brought together Middle Eastern countries that had normalized relations with Israel, as a coalition to deter Iran, and the United States held secret military talks with several countries in the region.
On September 16, 2022, twenty-two-year-old Mahsa Amini died from injuries sustained while in custody for allegedly violating Iran’s strict Islamic dress code, which requires women to wear hijabs. Her death sparked protests on a historic scale, with women burning headscarves in defiance of the state ‘morality police.’ Demonstrations quickly spread throughout the country and into schools, prisons, and sporting events, and Iranians living abroad led protests around the world. The Iranian regime cracked down on the protesters, killing at least 537 people, including children, during the months of resistance. In December, an Iranian official suggested the ‘morality police’ could be abolished, though the state never confirmed the move. Ultimately, the regime prevailed and subdued the protests in early 2023 after a series of executions of protesters. An environment of fear and intimidation persists, and the regime has barred women from accessing services if they do not comply with hijab requirements. In July 2023, Iran announced that the morality police had resumed hijab patrols; since then, women have faced arrest and forced psychiatric care, among other punishments, for violating the laws.
Meanwhile, stop-and-start negotiations throughout 2022 failed to achieve any breakthroughs on a return to the nuclear deal. In May 2023, China brokered a deal to restore official ties between Iran and Saudi Arabia, and Iran reopened its embassy in Riyadh. Iran has also pursued rapprochement with the UAE and expressed support for a regional dialogue in a bid to decrease its isolation. The thawing of regional ties provides hope for an easing of proxy wars, especially in Yemen. The Joe Biden administration has reportedly pursued an informal political deal to forestall escalation and achieve the release of political prisoners in negotiations in Oman.
However, Iran has continued military provocations in 2023, unveiling a new ballistic missile, seizing two tankers in April and May, and attempting to seize two more in July. In response, the United States sent F-16 fighter jets to the Persian Gulf, and more than three thousand Navy and marine troops, led by an aircraft carrier, sailed through the Suez Canal toward the area as part of a new maritime force.