Iran has been the thorn in the side of the West for decades, and tensions have only ramped up in recent years, as Iran continues to pursue a nuclear program that it insists is benign but that the West sees as a serious threat to global security. 

Iran's support of Syrian President Bashar al-Assad and his almost two-year-long campaign to crush opposition forces trying to overthrow his regime has also pegged it against Western countries, which are supporting the Syrian opposition.

It also remains locked in an escalating war of words and sabre-rattling with its biggest enemy, Israel. Israel has ramped up its rhetoric in the past year and repeatedly urged its Western allies to get tougher with Iran and prepare to launch pre-emptive military strikes against its nuclear facilities in order to slow down what it says is a rapidly progressing nuclear program.

The following is a timeline of key milestones in the history of Iran and its relations with the West.

Quick links

Space monkeys, Syria

Feb. 4, 2013 — Saeed Jalili, the head of Iran's National Security Council, publicly condemns  Israel's air strike against a convoy of anti-aircraft missiles in Syria that was suspected of being intended for the Lebanese militant group Hezbollah. Jalili made the comments during a three-day visit to Syria. He threatened retaliation against Israel for attacking Iran's ally and reiterated his country's support for the al-Assad regime, which  has been embroiled in a bloody civil war against opposition forces that want al-Assad to step down.

Jan. 28, 2013 — Iranian officials announce that the country's space agency has launched a monkey into space. The move was intended to help Iran eventually carry out a manned space flight. Iranian President Mahmoud Ahmadinejad has said he would like to be the country's first astronaut.

January 2013 — Iranian filmmaker Ataollah Salmanian announces that he has written a screenplay for a film to counter the "ahistoric" Hollywood film Argo, which tells the story of 20 American hostages who escaped Iran in 1979 with the help of the Canadian ambassador after the U.S. embassy in Tehran was occupied during the revolution. Iran's minister of culture and Islamic guidance, Mohammad Hosseini, called Argo, which was banned in Iran, "an offensive act" driven by "evil intentions."

To strike or not to strike

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Israeli Prime Minister Benjamin Netanyahu points to graphic illustrating Iran's progress toward developing nuclear weapons as he addresses the 67th United Nations General Assembly in New York on Sept. 27, 2012. (Lucas Jackson/Reuters)

Sept. 27, 2012  — Israeli Prime Minister Benjamin Netanyahu appears before the United Nations General Assembly to lay out his case for military action against Iran, which he said was nearing the final stages of being able to enrich uranium to the level necessary for building a nuclear bomb. "The relevant question is not when Iran will get the bomb. The relevant question is at what stage can we no longer stop Iran from getting the bomb," he told the UN. Netanyahu has clashed with U.S. President Barack Obama over the issue of pre-emptive strikes against Iran's nuclear facilities because Obama and his administration favour a diplomatic solution and are not yet prepared to abandon this option. Canada, meanwhile, has been more favourable to Netanyahu's position.

Sept. 7, 2012 — Canada suspends diplomatic relations with Iran and announces that will will expel Iranian diplomats from the country. Foreign Affairs Minister John Baird says the government has added Iran to the list of countries considered state sponsors of terrorism under the Justice for Victims of Terrorism Act. The government identified three main reasons for its decision to break off relations: Iran's support for Syrian President Bashar al-Assad's regime, its failure to comply with UN resolutions on its nuclear program and its threats against Israel.

March 5, 2012 — Strains in the historically close relationship between the U.S. and Israel come to the fore during Israeli Prime Minister Benjamin Netanyahu's visit to the U.S. Netanyahu stresses that Israel must remain "the master of its fate" and has a right to launch pre-emptive strikes against Iran if it feels its security is threatened by Iran's nuclear aspirations. Obama reiterates that the U.S. has Israel's back but clearly signals that it favours a diplomatic solution. A few days earlier, Obama tells The Atlantic magazine that while the U.S. is prepared to strike against Iran if necessary, military action at this time would be premature.

March 4, 2012 — Conservative opponents of Iranian President Mahmoud Ahmadinejad win a majority of seats in the parliamentary elections. The country's legislature cannot influence key foreign and security policy matters like the nuclear program but can affect the election of Ahmadinejad's successor. Ahmadinejad had clashed with his conservative rivals when he tried to change the political structure that subordinates the legislature and president to Supreme Leader Ayatollah Ali Khamenei and other religious leaders. Observers interpreted the election results as a show of support for the political status quo and a rejection of Western pressure on Iran to scale back its nuclear program.

Jan. 11, 2012 — A car bomb in Tehran kills a senior Iranian scientist who worked at the Natanz uranium enrichment facility in central Iran. Iranian officials blame the bomb on the U.S. and Israel.

Tougher sanctions

Dec. 26,  2011 —The U.S. warns Iran that it will take strong action if it makes good on its threat to close off the Strait of Hormuz in the Persian Gulf, a vital transportation route for about one-sixth of the world's oil. Iran's threat came in response to a tightening of Western economic sanctions against Iran.

Dec. 16, 2011  Russia's customs agency says that radioactive metal from the luggage of an Iranian passenger bound for Tehran had been seized at Moscow's Sheremetyevo airport after a radiation alert went on. Gauges showed that radiation levels were 20 times higher than normal, the agency says.

Dec. 1, 2011 — The U.S. Senate passes bill allowing the U.S. president to bar foreign financial institutions that do business with the Iranian central bank from having corresponding bank accounts in the U.S. If enacted, the legislation, which is opposed by U.S. President Barack Obama, would go into force in July 2012.

Nov. 28, 2011 — Hardline supporters of the Iranian regime ransack the British embassy in Tehran after the U.K. freezes $1.6 billion in Iranian assets and bars U.K. financial institutions from doing business with Iranian banks. In response, Britain cuts diplomatic ties with Iran and expels Iranian diplomats from the U.K. The attacks are believed to have been carried out by the Basij militia, the youth wing of Iran's elite military force, the Revolutionary Guard Corps.

Nov. 8, 2011 — The International Atomic Energy Agency releases a report suggesting Iran has been procuring equipment and conducting tests for the purpose of developing a nuclear weapons program. Several countries —mainly the U.S., the U.K. and Canada — react by imposing financial sanctions against Iran, freezing assets and barring financial trade with the country. The EU, however, falls short of barring imports of oil from Iran, which has some of the largest oil reserves in the world and is a key supplier to European countries such as Greece.  

Oct. 2011 —  Two Iranians are charged in U.S. federal court with plotting to assassinate the Saudi ambassador to the U.S. One of the men is reportedly a member of the Quds Force, an offshoot of the Revolutionary Guards that carries out foreign operations.

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Sarah Shourd, Shane Bauer and Josh Fattal at a news conference in New York on Sept. 25, 2011. The three Americans were accused of spying and imprisoned in Iran but claimed they had wandered into Iran accidentally while hiking in Iraq in 2009. (Jessica Rinaldi/Reuters)

Sept. 2011 — Two Americans convicted of spying in Iran and sentenced to eight years in prison are released on bail of around $500,000 US each and return to the United States. The two men and a third U.S. citizen were arrested on the Iran-Iraq border in July 2009. They said they were hiking and had crossed over into Iran accidentally. The third accused was released in September 2009, also on bail of $500,000 US. The 2011 release is seen as an effort to ease Iran's tensions with the West ahead of a meeting of the UN General Assembly.

Sept. 2011 —Iran announces that its Russian-built Bushehr nuclear plant has been connected to the national power grid after decades of delay. Construction on Bushehr, billed as the Middle East's first commercial nuclear plant, had first begun under the shah in 1975, but the project was stalled by the revolution, the Iran-Iraq war and opposition from the West.

Feb. 2011 — Iran sends two warships through the Suez Canal on their way to a training exercise in Syria, a move seen by many as a symbolic act of provocation aimed at Israel. It is believed to be the first time Iranian warships have been in the canal since the 1979 revolution.

Mid-Feb. 2011 — Opposition leaders Mir Hossein Mousavi and Mehdi Karroubi are placed under house arrest.

Cyberattack

Sept. 2010 — A destructive computer worm known as Stuxnet disables several centrifuges at the Natanz uranium-enrichment plant in Iran. The complexity of the cyberattack suggests it was orchestrated by at least one nation state and several experts believe it was a joint action by Israel and the U.S. intended to hobble Iran's nuclear program.

June 2010 — The UN Security Council imposes its fourth round of sanctions on Iran since 2006 after the  IAEA releases a report that says Iran has enough nuclear material to build two weapons. Brazil and Turkey vote against the resolution; Lebanon abstains.

May 2010 — Iran makes a deal, brokered by Brazil and Turkey, to send some of its low-enriched uranium to Turkey in exchange for fuel for its research reactor. The move falls short of satisfying Western powers, since Iran says it won't prevent it from continuing its own enrichment program.

Jan. 2010 — The U.S. announces it will dispatch Patriot defensive missiles to Qatar, United Arab Emirates, Bahrain and Kuwait, keep two ships in the Persian Gulf and deploy forces to protect oil installations in Saudi Arabia in order to deter a possible attack by Iran on U.S. allies in the Gulf.

Jan. 2010 — Nuclear physicist Masoud Ali-Mohammadi is assassinated in Tehran. Iran blames the bomb attack on foreign agents wanting to undermine Iran's nuclear program. Members of the Iranian opposition say it was meant as a warning to those who, like Ali-Mohammadi, had campaigned for opposition candidate Mir Hossein Mousavi in the last election.

The almost-revolution

Nov.  2009 — The IAEA passes a resolution condemning Iran for not revealing sooner that it was building a second nuclear enrichment site, located near the city of Qom.  Its main enrichment site is at Natanz. The agency says the fact it had lied about the Qom site, which the IAEA said was begun as early as 2002, indicates Iran may be hiding other enrichment facilities.

June 2009 — Mahmoud Ahmadinejad defeats popular opposition leader Mir Hossein Mousavi in a disputed presidential election. Massive protests erupt questioning the legitimacy of the election results. The regime's crackdown against the protests, considered to be the biggest show of opposition in 30 years and dubbed the Green Movement, attracts international attention after the death of a female protester named Neda Agha-Soltan is captured on video and posted on YouTube. Between 30 and 80 protesters are believed to have been killed and more than 1,000 wounded.

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Demonstrators in Paris hold placards bearing images of Neda Agha Soltan, a 27-year-old Iranian woman reportedly shot dead by security forces during an anti-government protest in Tehran in June 2009. Her death, caught on video, caused outrage and spurred protests around the world. (Jacques Brinon, File/Associated Press)

May 2009 — A U.S. State Department report dubs Iran the "most active state sponsor of terrorism."

Nov. 2008 — Ahmadinejad congratulates Barack Obama on his win in the U.S. presidential election. It's an unprecedented move for an Iranian leader.

July 2008 — Iran tests a long-range Shabab-3 missile that it claims could reach Israel.

March 2008 — Ahmadinejad visits Iraq, the first Iranian leader to do so in an official capacity since the revolution. While there, he calls for the withdrawal of foreign forces.

March 2008 — Conservatives win a two-thirds majority in elections that see 40 per cent of candidates disqualified from running by Iran's Council of Guardians.

Oct. 2007 — The U.S. imposes new sanctions intended to cut off access to the U.S. banking system to companies owned by Iran's Revolutionary Guard, which the U.S. accuses of supporting Iraqi insurgents. The sanctions are seen as the toughest since the revolution.

June 2007 —Riots erupt after Iran introduces fuel rationing amid fears of a new round of sanctions by the United Nations. The UN's nuclear watchdog agency had announced a month earlier that Iran was producing nuclear fuel and had more than 1,300 centrifuge machines that would enable it to develop nuclear weapons within three to eight years.

March 2007 — Fifteen British sailors and marines are held for 13 days after being captured by Iranian authorities in the Shatt al-Arab river between Iraq and Iran.

Start of Ahmadinejad era

Dec. 2006 — The UN Security Council votes to adopt sanctions on sales of nuclear materials and technology to Iran.

April 2006 — Iran announces it has successfully enriched uranium at a facility near the city of Natanz in central Iran.

Sept. 2005 — The IAEA finds Iran had not taken adequate measures with regard to the safeguarding, processing and use of nuclear material and was in violation of the Non-Proliferation Treaty.

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Iranian President Mahmoud Ahmadinejad soon after he was first elected in June 2005. (Damir Sagolj/Reuters)

June 2005 — Mahmoud Ahmadinejad, the hardline major of Tehran, wins presidential elections, dealing a blow to the reformers who had gained some ground in the last election.

Nov. 2004 — In an effort to avoid possible UN sanctions, Iran agrees to suspend its uranium enrichment activities after talks with ambassadors from Germany, Britain and France.

Nov. 2004  — Conservatives win Iran's parliamentary elections, rolling back gains made by reformers just four years earlier.

Dec. 2003 — A devastating earthquake hits the southeastern city of Bam, killing more than 30,000 people.

Nov. 2003 — Iran agrees to suspends it uranium enrichment program and allow tougher UN inspections of its nuclear facilities.

Jan. 2002 — U.S. President George W. Bush refers to Iran as one of three countries, along with Iraq and North Korea, that constitute an "axis of evil arming to threaten the peace of the world" in his first state of the union message.

June 2001 — Khatami is re-elected president.

Feb. 2000 — Reformers make sweeping gains in the parliamentary elections, winning 170 of 290 seats. It is the first time since 1979 that the hardliners lose control of the legislature.

Khomeini dies

Aug.-Sept. 1998 — Eight Iranian diplomats and a journalist are killed by Taliban fighters in Mazar-e-Sharif in northern Afghanistan. Iran positions thousands of troops along the Iran-Afghanistan border in response.

May 1997 — Mohammad Khatami, a moderate cleric and former cultural minister, is elected president on a reformist platform in a surprising upset. Despite energizing a large portion of the youth vote, Khatami was not able to push through his reform agenda during his two terms in office and was largely seen as an ineffective president.

May 1995 — U.S. adopts sanctions banning trade with and investment in Iran, in response to the ramping up of Iran's nuclear program and its support of organizations the U.S. considers terrorist entities such as Hezbollah and Hamas.

Aug. 1990 — Iraq invades Kuwait, whose borders Iraq had never accepted and which had refused to forgive Iraq's debt. Iran remains neutral in the conflict.

June 3, 1989 — Ayatollah Khomeini dies and is replaced by then president Ali Khamenei.

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In Iran, the supreme leader looms large. Here the faces of the Islamic republic's first supreme leader, Ayatollah Ruhollah Khomeini, right, and the current supreme leader, Ayatollah Ali Khamenei, are seen towering over President Mahmoud Ahmadinejad at a ceremony marking the anniversary of Khomeini's death on June 3, 2011. (Morteza Nikoubazl)

Feb. 14, 1989 — Ayatollah Khomeini issues a religious fatwa calling for the death of British author Salman Rushdie over his book The Satanic Verses, which the Iranian regime deems blasphemous against Islam's prophet, Muhammad. Britain suspends diplomatic relations with Iran and offers protection to Rushdie. The fatwa was eased somewhat in 1998 under the more reformist government of President Mohammad Khatami, but more hardline leaders renewed calls for the writer's death in the late 2000s.

July 1988 — Iran and Iraq sign a UN-brokered ceasefire agreement, ending eight years of war.

July 1988 — A U.S. warship patrolling the Persian Gulf mistakes an Iranian passenger jet for an F-14 fighter and shoots it down, killing 290 passengers and crew. Iran vows to "avenge the blood of our martyrs."

1987 — British chargé d'affaires Edward Chaplin is kidnapped in Tehran by revolutionary guards and held for 24 hours over Britain's perceived support of Iraq. The UK withdraws all staff.

1985 — In what became known as the Iran-Contra Affair, the U.S. made a deal to secretly sell weapons to Iran in exchange for the release of hostages being held by the Iranian-backed group Hezbollah in Lebanon. Iran needed the weapons to fund its war with Iraq, and the U.S., which was officially forbidden from selling arms to Iran, diverted part of the secret funds to CIA-backed guerillas in Nicaragua known as the Contras, who were trying to overthrow the leftist Sandinista regime. In the end only three U.S. hostages of several dozen were released — and three more were taken not long after.

Jan. 20, 1981 — The 52 remaining U.S. embassy hostages are released on the day of U.S. President Ronald Reagan's inauguration.

Hostage crises, Iran-Contra

1980-88 — Iran-Iraq war. In September 1980, Iraqi forces invaded Iran, whose new post-revolution Islamist government was seen as a threat by Iraq's president, Saddam Hussein. The invasion set off a brutal eight-year-long conflict that devastated both countries and ultimately ended in a draw. Hundreds of thousands of people died — possibly as many as 1.5 million. The U.S. under the Reagan administration sided with Iraq in the conflict, sharing intelligence and providing food credits and funds.

July 1980 —The shah dies of cancer in exile in Egypt.

May 1980 — Iranian embassy in London is attacked by Iraqi-backed opponents of the Khomeini regime who take several hostages. After six days and the death of one of the hostages, British SAS forces storm the building. One hostage and five gunmen are killed in the raid. 

April 25, 1980 — A secret attempt to free the U.S. embassy hostages fails spectacularly. Two of the American helicopters charged with carrying out the rescue run into engine trouble and a third is damaged during a landing. The mission is aborted, but while departing two helicopters crash, killing eight U.S. soldiers. The incident is a major blow for the administration of U.S. President Jimmy Carter, who suffers a massive defeat in the presidential election a few months later.

April 7, 1980 — The U.S. cuts all diplomatic ties with Iran.

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One of the several dozen people who were taken hostage at the U.S. Embassy in Tehran in 1979 is displayed before a crowd outside the embassy on Nov. 9, 1979. Fifty-two of the hostages were held for 444 days before being released. (File photo/Associated Press)

Jan. 1980 — Abolhasan Bani-Sadr, an economist and anti-shah activist who worked alongside Khomeini in exile in France and returned with him after the revolution, is elected president of the new republic. A year and a half later, he is impeached after criticizing some ministers, warning of needed reforms to the economy and armed forces and opposing the U.S. embassy hostage taking. He fled to France after Khomeini tried to have him arrested for treason.

Nov. 14, 1979 — U.S. President Jimmy Carter freezes all Iranian assets in U.S. banks and their subsidiaries abroad.

Nov. 4 1979 — Islamic revolutionaries take more than 60 Americans hostage at the U.S. embassy in Tehran, demanding the extradition of the shah, who was in the U.S. undergoing cancer treatment, to Iran to stand trial. Some hostages are released but 52 remain held for 444 days.  

April 1, 1979 — The new Islamic Republic is declared after a national referendum on whether or not to make Iran an Islamic republic. A committee of experts is convened to draft the new constitution, and it is this committee, made up in large part of Shia clerics and members of the Islamic Republican Party, that establishes the cleric-dominated system of rule and declares Khomeini the first supreme leader of the new theocratic republic.

Feb. 1979 – Exiled Islamic religious leader Ayatollah Ruhollah Khomeini returns to Iran and assumes control of the country.

Jan. 16, 1979 — With opposition getting fiercer, the shah and his wife flee to Egypt.

The shah clamps down

Sept. 1978 — The shah imposes martial law in the face of growing demonstrations and strikes opposing his authoritarian rule.

1968 —  Iran signs the Nuclear Non-Proliferation Treaty.

Nov. 1964 — Khomeini is sent into exile, from where he continues to denounce the shah through writings and lectures.  

June 1963 — Ruhollah Khomeini, a Shia scholar and vocal critic of the Western-backed regime of the shah, is arrested after making a speech denouncing the shah and U.S. influence in Iran.

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The Shah of Iran Reza Pahlavi and his wife, Empress Farah Diba, during their vacation at the villa of King Hassan II in Marrakesh, Morocco, in 1979, the year they fled Iran in the face of growing opposition to the shah's autocratic rule. (Randy Taylor/Associated Press)

Jan. 1963 — The shah launches a series of economic, land and social reforms aimed at Westernizing the country and known as the White Revolution. Those who oppose the reforms are ruthlessly silenced with the aid of the shah's secret police force, SAVAK. 

1953 — After a failed attempt to dismiss Prime Minister Muhammad Mossadegh, the shah flees to Rome. A few days later, the  U.S. and U.K. orchestrate a coup that ousts Mossadegh and installs the shah as the new leader, hoping he'll serve as a bulwark against Soviet influence in the Middle East

1951 — Prime Minister Muhammad Mossadegh oversees the nationalization of the oil industry, dominated by the Anglo-Iranian Oil Company. Britain responds by imposing a trade embargo on Iran.

1950 — Prime Minister Ali Razmara is assassinated and replaced by nationalist Muhammad Mossadegh, a government minister during the Qajar era and married to Qajari princess Zia al-Saltaneh.

1941 — Shah Mohammed Reza Pahlavi takes power after his father is forced to abdicate by the Allied powers over his too-cozy relations with Germany.

1921-1941  — Reza Khan, an officer of the Persian Cossack Brigade, leads a coup against the Qajar dynasty and in 1925 declares himself the shah and establishes the Pahlavi dynasty. In the following years, he changes the name of the country from Persia to Iran and pursues a program of secularization.