History of Iran: From Persia to present

For most of history, the tract of land now called Iran was known as Persia. It wasn't until 1935 that it adopted its present name.

Early Persia was a formidable empire, whose vast plateau rimmed by mountain ranges, was variously invaded by Arabs, Turks and Mongols.

The discovery of oil in the early 20th century generated international interest in the nation, particularly Great Britain and Russia. A 1907 Anglo-Russian agreement divvied up Iran into spheres of influence, though it was later annulled after the First World War.

The United States became increasingly interested in Iran following the Second World War, particularly its oil reserves.

In 1953, the U.S. and Britain helped orchestrate a coup d'etat to oust Prime Minister Mohammed Mosaddeq, bringing the pro-Western monarch, Shah Mohammad Reza Pahlavi, back to power.

In the years that followed, Iran forged closer ties with Washington, receiving large amounts of military and economic aid from America until the late 1960s. Iran began ramping up its defence budget, and with the help of American and British defence programs, it became one of the region's strongest military powers.

Iranian revolution

The country also saw increased Westernization, much to the dismay of the clergy who denounced the pro-Western policies and secularization.

Rising discord with the hereditary monarch, known as the shah, marked the early 1960s.

During the 1970s, Shah Reza Pahlavi faced growing opposition led by exiled spiritual leader Ayatollah Ruhollah Khomeini.

After years of tenuously holding onto power with the backing of the U.S., Pahlavi was ousted during the 1979 Islamic revolution and Khomeini came to power after returning from years in exile in France.

With that, the pro-West regime of the shah gave way to an official anti-American stance that was openly encouraged by the mullahs and Iran became an Islamic republic.

Under a new constitution, a popularly elected president served as head of government but the highest state authority became the Supreme Leader, a powerful post filled by a cleric and empowered to name leaders of the armed forces, the chief judge and other high ranking officials.

Hostage-taking, war with Iraq

When the deposed Shah was temporarily let into the U.S. for medical treatment for cancer, Islamic students back home demanded he be extradited to stand trial in Iran. Furious by a lack of action, the students and militants stormed the U.S. Embassy in Tehran on Nov. 4, 1979, holding more than 50 people hostage.

The hostage taking lasted 444 days, and included a failed rescue attempt. The situation strained relations between the two countries. Resolution came only when Ronald Reagan was inaugurated as U.S. president on Jan. 20, 1981, and the hostages were let go.

Meanwhile, even as Iran was occupied with the hostage-taking, tensions with its neighbour, Iraq, were escalating.

Iraq invaded Iran in the fall of 1980 over a conflict sparked in part by a disagreement over the border in the Shatt-al-Arab waterway area.

The bloody, eight-year conflict would end up resolving little but took a toll on the nation. Reliable casualty counts are hard to come by, but estimates range from 300,000 to two million.

Over the years, the leadership of the Islamic republic has remained overwhelmingly conservative — true to the roots of the revolution, which came from the conservative countryside and the seminaries of the holy city of Qum.

Efforts by moderates to modernize some of Iran's institutions in the late 1990s were consistently derailed and undermined by more conservative elements. And the conservatives remain firmly in power even now.

Tensions over nuclear plans

Iran's nuclear installations and lack of disclosure during international inspections have triggered fears that the country is developing nuclear weapons. Tehran claims its efforts are peaceful and aimed at building an atomic power station.

In 1995, the U.S. suspended all trade with Iran over its nuclear ambitions and alleged support of terrorist groups.

Over the years, the U.S. increasingly denounced Iran for pursuing nuclear weapons and in a 2002 speech by then U.S. president George W. Bush he grouped Iran among the "axis of evil." Tensions with the U.S. also ramped up after the U.S. invaded Iraq in March 2003.

When Mahmoud Ahmadinejad, the former hardline mayor of Tehran, won the 2005 presidential election, he vowed to press on with the country's nuclear agenda.

Ahmadinejad has repeatedly riled the world with his controversial remarks, denouncing the Holocaust as a deception and issuing biting anti-Israel comments.

In 2006, Iran announced it had successfully produced enriched uranium. Calls for Iran to halt its nuclear plans did little and sanctions were imposed.

With a worsening economic situation, due in part to sanctions and falling oil prices, support for Ahmadinejad has diminished in recent years.

Reform candidate Mir Hossein Mousavi, a former prime minister, hoped to capitalize on that in the June 2009 presidential elections, but Ahmadinejad announced a landslide victory.

Mousavi's representatives alleged electoral fraud, and in the days that followed, tens of thousands of supporters from both sides took to the street in deadly protests.

One of those killed in the demonstrations and security crackdown was an apparent innocent bystander, Neda Agha-Soltan, whose final seconds on June 20 were captured on amateur video and viewed around the world.

Neda, as she was known, became in death an icon for opposition protesters. Ahmadinejad has called for an investigation of her death, allegedly at the hands government militia.

Even if answers are found, however, the undercurrent of public discontent could last for some time.