There was a time when the United States and Iran worked closely together. Washington backed Iran’s monarchy. Tehran supplied oil and access in a tense global environment.
By early 2026, the relationship had worsened into direct military conflict after decades of hostility.This is the clear timeline of how that shift unfolded.
Chapter 1: Oil, Empire And Early Alliances (1901–1946)
In 1901, British investor William Knox D'Arcy secured a deal with Iran’s king, Mozaffar ad-Din Shah Qajar, to explore oil. Iran would receive 16 percent of profits.
In 1908, oil was discovered in southwest Iran. It was the first major oil find in the Middle East. The discovery led to the formation of the Anglo-Persian Oil Company, which later became BP.
During the Second World War, Britain and the Soviet Union occupied Iran to secure supply routes. The occupation caused inflation and severe shortages.
After the war in 1946, Soviet troops delayed their withdrawal. Iran took the issue to the United Nations Security Council. The United States backed Iran. The Soviets finally pulled out.
At this stage, Washington saw Iran as strategically important because of its oil and location between the Soviet Union and the Indian Ocean.
Chapter 2: The Coup That Changed Everything (1951–1955)
In 1951, Iran’s Prime Minister Mohammad Mossadegh nationalised the oil industry. He said foreign companies were taking most of the profits.
Britain imposed a boycott. The United States later joined. Iran’s economy suffered.
In 1953, US and British intelligence carried out a covert operation known as Operation Ajax. Mossadegh was removed from power.
The Shah, Mohammad Reza Pahlavi, regained control. US companies secured a share of Iranian oil.
In 1955, Iran and the US signed the Treaty of Amity to strengthen economic ties and protect citizens and business interests.
Publicly, relations looked strong. Inside Iran, resentment over the coup remained.
Chapter 3: Revolution And Hostages (1960s–1981)
By the 1960s and 1970s, opposition to the Shah grew. Cleric Ruhollah Khomeini criticised his rule and Western ties.
In 1979, the Shah left Iran. The Islamic Revolution followed. Iran became an Islamic Republic.
Later that year, students stormed the US Embassy in Tehran. They took 52 Americans hostage for 444 days. Diplomatic relations ended. Distrust deepened.
Chapter 4: War And Direct Clashes (1980–1989)
In 1980, Iran went to war with Iraq. The United States initially said it was neutral but provided support to Iraq, including intelligence and military aid.
In 1988, a US Navy ship mistakenly shot down Iran Air Flight 655, killing 290 people. Washington called it an accident. Iran condemned it.
By the end of the decade, hostility was entrenched.
Chapter 5: Sanctions And The Nuclear Dispute (1990s–2000s)
In the 1990s and 2000s, the US labelled Iran a state sponsor of terrorism and expanded sanctions.
In 2002, US President George W. Bush described Iran as part of an “axis of evil”.
Iran pursued nuclear technology, saying it was for peaceful energy. The US and others feared weaponisation.
The United Nations imposed sanctions. The US added its own. Iran’s economy felt mounting pressure.
Chapter 6: The Nuclear Deal And Its Collapse (2015–2018)
In 2015, Iran and six world powers signed the Joint Comprehensive Plan of Action. Under the deal, Iran limited uranium enrichment and reduced its nuclear stockpile. In return, sanctions were lifted.
US President Barack Obama said the agreement reduced nuclear risk.
In 2018, President Donald Trump withdrew the United States from the deal and reimposed sanctions. Iran gradually reduced its compliance.
Tensions rose again.
Also Read: Who Was Ayatollah Ali Khamenei?
Chapter 7: Assassinations And Regional Escalation (2020–2024)
In January 2020, a US drone strike killed Iranian general Qasem Soleimani in Iraq.
Iran responded with missiles aimed at US military bases. Both sides avoided a wider war, but hostility deepened.
Iran continued advancing uranium enrichment beyond JCPOA limits. Western governments monitored the programme closely.
Chapter 8: The 2025 Escalation
In 2025, tensions rose sharply around Iran’s nuclear work and regional influence.
Israeli officials said Iran had enriched uranium to approximately 60 percent, close to weapons-grade levels.
In June 2025, the United States carried out strikes on Iranian nuclear facilities, citing concerns over rapid enrichment and regional security.
Iran condemned the strikes and responded with missile fire at a US base in the Gulf. Regional airspace closures and higher oil prices followed.
Attempts at a ceasefire eased immediate hostilities, but distrust remained high.
Also Read: How World Leaders Reacted to the US-Israel Strikes
Chapter 9: February 2026 Attack
On 28 February 2026, the United States and Israel launched coordinated military strikes on multiple Iranian targets. Officials said the operation targeted nuclear and strategic facilities.
Iran’s Supreme Leader Ali Khamenei was killed in the strikes, according to statements from Iranian officials and multiple international reports.
Iran said it had been hit in what it called a violation of its sovereignty. The strikes also hit civilian infrastructure, including a girls’ school in Minab province, resulting in extensive casualties. Independent verification of exact numbers varied between sources.
Iran responded with ballistic missile and drone attacks on Israeli and US military sites across the region. Airspace disruptions and regional alerts followed.
Oil markets spiked on fears of wider conflict.
US and Israeli officials said the strikes were preventive and aimed at stopping Iran from nearing nuclear weapon capability. Iran said it would not abandon its nuclear programme and vowed retaliation.
