The relationship between the United States and Iran has been defined by mistrust, miscalculations, and moments of intense confrontation. What began as a partnership during the early 20th century evolved into one of the most enduring geopolitical rivalries of the modern era. The following timeline offers an in-depth look at the key moments that shaped this volatile relationship and the forces that continue to drive conflict between the two nations.
1953 – Operation Ajax: US and UK Restore the Shah in Iran
In the early 1950s, Iran’s Prime Minister Mohammad Mossadegh sought to nationalize the country’s oil industry, which had been under British control for decades. His move was seen as a threat to Western interests. In response, the U.S. Central Intelligence Agency (CIA) and Britain’s MI6 orchestrated Operation Ajax, a covert mission that overthrew Mossadegh and restored the Shah, Mohammad Reza Pahlavi, to full power.
Although the operation secured Western control over Iranian oil in the short term, it left lasting damage. For many Iranians, it confirmed that the U.S. was more interested in safeguarding its geopolitical interests than supporting democratic ideals. The bitterness surrounding the coup and its aftermath became a defining grievance that would shape Iran’s view of the West for generations to come.
1957– U.S. Atoms for Peace program
The Shah of Iran pursued nuclear energy with strong backing from the U.S. and its Western allies. As part of President Eisenhower’s Atoms for Peace initiative, the two countries signed a civil nuclear agreement, leading the U.S. to provide Iran with a research reactor and enriched uranium.
The Atoms for Peace program provided the foundations for Iran’s nuclear program by providing key nuclear technology and education.
At the time, Iran’s program was seen as peaceful and strategic. Ironically, this early collaboration laid the groundwork for today’s nuclear standoff, as infrastructure from that era remains central to current tensions.
1979 – The Islamic Revolution
After years of growing opposition to the Shah’s authoritarian rule, fueled by economic inequality, human rights abuses, and religious discontent, the Iranian Revolution reached its peak in early 1979. The Shah fled the country, and Ayatollah Ruhollah Khomeini returned from exile to lead the newly established Islamic Republic.
The revolution marked a dramatic ideological break. The U.S., once Iran’s closest ally, was now labelled the “Great Satan.” The Iranian regime positioned itself in direct opposition to American influence, championing a theocratic model rooted in Islamic principles and fiercely critical of Western imperialism.
1979–1981 – The U.S. Embassy Hostage Crisis
In November 1979, after the U.S. allowed the exiled Shah to enter the country for cancer treatment. Iranian students stormed the U.S. Embassy in Tehran, taking 52 American diplomats and citizens hostage.
The crisis lasted 444 days and became a defining event in U.S. foreign policy. It humiliated the Carter administration and severely damaged bilateral relations. To this day, it remains one of the most visible symbols of the collapse in trust between the two nations.
In response, the U.S. froze billions in Iranian assets and broke off diplomatic ties—measures that remain in place in many forms to this day.
1980s – Proxy Wars and Poisonous Warfare
Throughout the 1980s, the U.S. and Iran found themselves on opposing sides of the Iran–Iraq War (1980–1988). The United States offered covert and publicly supported Saddam Hussein’s Iraq, despite knowing Iraq used chemical weapons.
The U.S. also escalated naval presence in the Persian Gulf to protect oil shipping lanes, leading to direct skirmishes with Iranian forces.
In 1988, a tragic incident occurred: the USS Vincennes mistakenly shot down Iran Air Flight 655, killing all 290 civilians on board. The U.S. paid the affected families $61.8m as compensation and called it an accident. Iran never accepted the explanation, and the memory of that event continues to fuel distrust.
1990s – Sanctions and Isolation
In 1990’s the United States significantly escalated its economic pressure on Iran through a new wave of sanctions. President Bill Clinton, citing concerns over Iran’s advancing nuclear program and its alleged support for militant groups such as Hezbollah, Hamas, and Palestinian Islamic Jihad, issued executive orders barring American companies from investing in or trading with Iran.
Around the same time, Congress passed the Iran and Libya Sanctions Act (ILSA), which extended penalties to foreign firms that invested more than $20 million annually in Iran’s energy sector or provided it with advanced weaponry.
These measures marked a turning point in U.S. policy, transforming its sanctions regime from a primarily bilateral effort into one with global reach and enforcement, aiming to isolate Iran both economically and diplomatically.
2000s – The Nuclear Question Emerges
The early 2000s marked the beginning of global concern over Iran’s nuclear ambitions. Iran insisted its program was for peaceful purposes, but Western powers remained unconvinced.
Tensions escalated when President George W. Bush, in his 2002 State of the Union address, placed Iran in the “Axis of Evil”, alongside Iraq and North Korea.
In 2006, Iran’s refusal to halt uranium enrichment led to a series of U.N. Security Council sanctions. International pressure mounted, but Iran remained defiant, framing its nuclear program as a symbol of national pride and independence.
2015 – The Iran Nuclear Deal (JCPOA)
In a rare diplomatic breakthrough, Iran and six world powers, including the U.S., reached the Joint Comprehensive Plan of Action (JCPOA). The deal limited Iran’s nuclear program by capped Iran’s enrichment at 3.67 percent in exchange for the lifting of economic sanctions.
It was seen as a historic agreement that reduced the risk of conflict and opened the door for further engagement. For a brief moment, it appeared that relations could improve. However, not everyone supported the deal, particularly conservatives in the U.S. and hardliners in Iran, who saw it as either too lenient or too compromising.
2018 – Trump Withdraws from the JCPOA
In 2018, President Donald Trump unilaterally withdrew the U.S. from the nuclear deal, calling it “fatally flawed.” His administration reimposed sweeping sanctions under a “maximum pressure” campaign.
Iran responded by gradually rolling back its compliance, enriching uranium beyond JCPOA limits, and reasserting its nuclear capabilities.
The withdrawal reignited tensions, crippled Iran’s economy, and pushed both sides back toward confrontation.
2020 – The Assassination of Qassem Soleimani
In January 2020, the U.S. conducted a drone strike that killed General Qassem Soleimani, a top commander of Iran’s Quds Force. Soleimani was personally sanctioned by the United Nations and the European Union, and was designated as a terrorist by the United States in 2005.
Under his leadership, Iran had bolstered Hezbollah in Lebanon and other pro-Iranian militant groups. Soleimani’s killing marked a major escalation in tensions between Washington and Tehran.
2021–2023 – Diplomatic Deadlock
Under President Joe Biden, efforts were made to re-enter the JCPOA, but talks stalled. Distrust was high on both sides. Iran, demanded a full sanctions relief before taking any steps. The U.S., refused to lift sanctions without concrete commitments. The deadlock left the nuclear issue unresolved.
Also Read: Trump Enters Iran-Israel War Without an Exit Plan: Escalation Risks Global Fallout
2025 – U.S. Strikes Iran
In March, President Donald Trump sent a letter to Iran’s Supreme Leader, Ayatollah Ali Khamenei, proposing a new nuclear agreement with a 60-day deadline. However, Khamenei rejected the proposal, stating that the U.S. was not interested in genuine negotiations but in imposing demands.
Despite this, informal talks quietly began in Oman and Italy, with Muscat acting as a mediator. Trump later pointed that his team was “very close” to securing a deal and warned Israel against initiating military action. Tehran also expressed cautious optimism but remained firm on its right to enrich uranium—a key sticking point in the negotiations.
Tensions peaked when, just a day before the sixth round of U.S.–Iran discussions, Israel launched airstrikes across Iranian territory. In the aftermath, and following a series of attacks linked to Iranian proxy groups and the apparent collapse of backchannel diplomacy, the United States launched targeted strikes on Iran’s nuclear infrastructure in Fordow, Natanz, and Esfahan.
The move, framed as a response to escalating security threats and in defence of Israel, triggered immediate fears of a broader regional conflict.
The relationship between the United States and Iran has been defined more by turbulence than by trust. Although Trump has announced a complete and total ceasefire between Isreal and Iran, but the stakes are high, and the choices made in the coming months may determine whether this long-standing rivalry edges toward reconciliation or spirals further into open conflict.