On February 28, the United States and Israel launched a new military operation against Iran. It marks the culmination of decades of tensions between two countries that were once allies. As recently as the mid-20th century, Washington actively supported the Iranian monarchy, helped develop civilian nuclear energy, and sold modern weapons to Tehran. However, the Islamic Revolution of 1979 transformed Iran from a key U.S. partner in the Middle East into one of its main adversaries. Today, after the assassination of Supreme Leader Ali Khamenei and the resumption of hostilities, diplomatic relations between the two countries appear definitively shattered. Here is how the confrontation between Iran and the United States evolved — from cooperation to direct military conflict.
1953. 1953. The Coup and the Return of the Shah
The modern history of U.S.–Iran relations effectively begins with the 1953 coup. British and American intelligence services carried out Operation Ajax, which overthrew Prime Minister Mohammad Mossadegh. Two years earlier, Mossadegh had nationalized Iran’s oil industry, which had been controlled by the British company British Petroleum. After the coup, power returned to Shah Mohammad Reza Pahlavi, who restored Western companies’ influence over the country’s oil sector. These events triggered strong anti-American sentiment within Iranian society, as many Iranians viewed the United States as responsible for interfering in the country’s internal affairs.
1950s–1970s. Alliance and Strategic Partnership
Despite growing public discontent, the Shah’s Iran became one of the United States’ main allies in the Middle East. In 1957, Washington and Tehran signed an agreement to develop civilian nuclear energy under President Dwight Eisenhower’s “Atoms for Peace” initiative. The United States supplied Iran with a research reactor and enriched uranium.
In 1968, both countries also signed the Nuclear Non-Proliferation Treaty.
By the early 1970s, the alliance had reached its peak. During President Richard Nixon’s visit to Tehran in 1972, Washington promised to supply Iran with the most advanced weapons systems. The Shah spent more than $16 billion on military equipment, including F-14 interceptor fighters. Iran was considered a cornerstone of the U.S. security strategy in the Persian Gulf.
1979. 1979. The Islamic Revolution
February 1979 marked a turning point in the country’s history. After months of protests, the Shah left Iran and Ayatollah Ruhollah Khomeini returned from exile. Iran transformed from a pro-Western monarchy into an Islamic republic built on a theocratic system. The new leadership immediately adopted a strongly anti-American stance. Khomeini popularized the slogans “Death to America” and “Death to Israel.”
In November 1979, revolutionary militants stormed the U.S. embassy in Tehran. Fifty-two American diplomats were taken hostage. The hostage crisis became one of the most dramatic episodes of the late Cold War and permanently shattered relations between the two countries.
1980. 1980. Diplomatic Break
The United States attempted to rescue the hostages through the military operation Eagle Claw, but the mission failed due to technical problems and a sandstorm. Following the failed rescue attempt, President Jimmy Carter severed diplomatic relations with Iran and imposed a trade embargo. That same year, Iran was drawn into an eight-year war with Iraq. During the conflict, the country became almost completely isolated internationally.
1980s–1990s. Sanctions and Persistent Tensions
In 1981, the American hostages were finally released after the signing of the Algiers Accords. The United States agreed to unfreeze certain Iranian assets and promised not to interfere in Iran’s internal affairs. Nevertheless, relations continued to deteriorate.
In 1984, Washington placed Iran on its list of state sponsors of terrorism.
In 1988, the U.S. cruiser USS Vincennes shot down an Iranian civilian airliner over the Strait of Hormuz, killing all 290 people on board.
In the mid-1990s, the administration of President Bill Clinton imposed sweeping sanctions on Iran’s oil industry and banned American companies from investing in the country.
The 2000s. The Nuclear Crisis
In 2002, U.S. President George W. Bush labeled Iran part of the “axis of evil,” alongside Iraq and North Korea. That same year, revelations about secret nuclear facilities in Natanz and Arak triggered an international crisis over Iran’s nuclear program.
In 2009, Western countries announced the existence of another uranium enrichment facility hidden inside a mountain near Fordow.
2015. 2015. The Nuclear Deal
After years of negotiations, Iran and six world powers: the United States, Russia, China, France, the United Kingdom, and Germany, reached an agreement on Iran’s nuclear program. Tehran agreed to limit uranium enrichment and allow international inspections of its facilities. In exchange, part of the sanctions imposed on the country were lifted.
2018. 2018. The U.S. Withdrawal from the Deal
President Donald Trump unilaterally withdrew from the agreement, calling it “the worst deal ever.” The United States reimposed severe economic sanctions on Iran and launched a campaign of “maximum pressure.” In response, Tehran resumed uranium enrichment and gradually began abandoning its commitments under the agreement.
2020. 2020. The Killing of General Soleimani
In January 2020, the United States killed General Qassem Soleimani, one of Iran’s most influential military commanders. Tehran retaliated with missile strikes against U.S. bases in Iraq, although a large-scale war was ultimately avoided.
2025. 2025. A Short War
After Donald Trump returned to the White House, pressure on Iran intensified significantly. In the summer of 2025, Israel launched a series of strikes against Iranian nuclear facilities. The United States later joined the operation. American B-2 bombers struck several major nuclear sites, including Natanz, Fordow, and Isfahan. Trump declared that Iran’s nuclear program had been completely destroyed and soon imposed a ceasefire.
2026. 2026. Protests and a New War
At the end of 2025, large protests erupted in Iran due to the economic crisis and the collapse of the national currency. The demonstrations quickly took on a political dimension. U.S. President Donald Trump openly supported the protesters and stated that the United States was ready to help the Iranian people. Iranian authorities violently suppressed the demonstrations, deploying forces from the Islamic Revolutionary Guard Corps.
In February 2026, Washington and Tehran attempted to resume negotiations on a new nuclear deal, but the positions of the two sides remained irreconcilable.
On February 28, the United States and Israel launched a new military operation against Iran. According to Donald Trump, the objective was to eliminate the threat posed by the Iranian regime. After the assassination of Supreme Leader Ali Khamenei, Iranian authorities announced that they would no longer conduct any negotiations with Washington.
Thus, a conflict that has been building for decades has entered its most dangerous phase: a direct military confrontation between Iran and the United States.
