1905: Constitutional Revolution begins amid struggle for independence from Russian and British control; the first parliament is formed in 1906 under the new constitution, which limits power of the Qajar monarchy.

1907: Anglo-Russian Entente divides Persia into three spheres: British, Russian and neutral.

1908: British geologists discover oil in the neutral sphere of Persia; Anglo-Persian Oil Company (later the Anglo-Iranian Oil Company) is formed.

1926: Cossack Brigade officer Reza Khan (1878–1944) overthrows the Qajar Dynasty and is crowned Shah of Persia.

1935: Reza Shah asks foreign delegations to refer to the country as Iran, a name dating from ancient times, rather than Persia.

1941: Concerned about Iran’s pro-German leanings in World War II, Britain and the Soviet Union occupy Iran and replace Reza Shah with his son, Mohammad Reza Pahlavi (1919–1980).

1951: Mohammad Mossadegh (1882–1967) is elected prime minister; he nationalizes the British-controlled Iranian oil industry and curbs powers of shah.

1953: Mossadegh is overthrown in a coup d’état backed by the Central Intelligence Agency and the British intelligence agency MI6.

1957: Shah and President Dwight Eisenhower sign a civil nuclear cooperation agreement under the U.S. Atoms for Peace program; the Central Treaty Organization’s Institute of Nuclear Science moves headquarters from Baghdad to Tehran.

1959: Tehran Nuclear Research Center (TNRC) is established at Tehran University.

1963: Shah initiates the White Revolution, a modernization program for economic, social, and political reform; riots follow arrest of Ayatollah Ruhollah Khomeini (1902–1989) for anti-shah speech.

1964: Khomeini begins fourteen years in exile in Najaf and Paris.

1967: Tehran Research Reactor (TRR) begins operation at TNRC.

1968: Iran signs the Nuclear Non-Proliferation Treaty (NPT) on the opening day for signatures; it is ratified by parliament in 1970.

1972: Iran signs the Biological Weapons Convention; it is ratified by parliament in 1973.

1974: Atomic Energy Organization of Iran (AEOI) is established, and Esfahan Nuclear Technology Center is set up to develop nuclear technology; Iran signs a $1.2 billion deal with the France-based Eurodif consortium to enrich uranium on French soil and supply fuel to the TRR and future nuclear power facilities; Iran signs agreements with West German and French companies to build reactors in Bushehr and Bandar Abbas; Iran concludes NPT Safeguards Agreement, enabling the International Atomic Energy Agency (IAEA) to independently verify the accuracy of Iran’s declarations about its nuclear material and activities.

1975: Shah states that Iran has “no intention of acquiring nuclear weapons but if small states began building them, Iran might have to reconsider its policy”; Secretary of State Henry Kissinger signs U.S.-Iran Nuclear Cooperation memorandum endorsing $6.4 billion deal for six to eight nuclear reactors.

1978: At a New Year’s Eve state dinner in Tehran, President Jimmy Carter toasts shah as “island of stability in a turbulent corner of the world”; in January, seminary students in holy city of Qom demonstrate after an article in leading state newspaper Ettelaat ridicules Khomeini; police kill several protestors; ranking cleric declares shah’s regime “un-Islamic”; incident triggers year-long cycle of religious demonstrations; in September, police kill hundreds of demonstrators in Jaleh Square massacre in Tehran; in October, public sector strikes paralyze economy.

January 16, 1979: Shah flees Iran; mass demonstrations demand resignation of government of Prime Minister Shapour Bakhtiar (1914–1991).

February 1, 1979: Khomeini returns to Iran as leader of Iran’s revolution.

February 11, 1979: Khomeini names Mehdi Bazargan (1907–1995) of Iran Freedom Movement as prime minister; Bakhtiar government collapses.

March 30, 1979: Iranians abolish monarchy and approve Islamic republic in referendum.

November 4, 1979 Iranian protestors seize the U.S. Embassy in Tehran and hold fifty-two Americans as hostages for 444 days.

November 12, 1979: U.S. Proclamation 4702 imposes an Iranian oil import ban.

November 14, 1979: U.S. Executive Order 12170 freezes $12 billion in Iranian assets held in the United States.

1980:  U.S. Executive Order 12205 prohibits U.S. commercial trade with Iran, with the exception of clothing donations, food, and medical supplies; U.S. Executive Order 12211 prohibits the import of Iranian goods or services and financial transactions with Iran; Iraqi leader Saddam Hussein, with support from Western nations, launches an invasion of Iran, marking the beginning of the Iran-Iraq War.

1981: U.S. and Iran sign the Algiers Accords, under which U.S. unfreezes Iranian assets, revokes previous executive orders, and commits not to intervene in Iran’s internal affairs, upon the release of U.S. hostages; AEOI announces discovery of four uranium deposits in Iran.

1982: Iran establishes Hizbollah organization in Lebanon amid Israel’s invasion of Lebanon; group leads resistance to the ensuing eighteen-year Israeli occupation.

1983: Iran asks IAEA to provide technical assistance with the production of uranium hexafluoride (UF6), a gas compound used for uranium enrichment.

1984: Iraqi forces bomb the Bushehr site; China assists Iran in establishing a nuclear research center in Esfahan; State Department designates Iran as a state sponsor of terrorism; U.S. enforces sanctions on Iran including: restrictions on U.S. foreign assistance, a ban on defense exports and sales, limits on exports of dual-use items, and miscellaneous financial restrictions.

1986: Revelations emerge in Iran-Contra Affair that the President Ronald Reagan administration secretly provided weapons to Iran in exchange for the release of Americans held hostage by pro-Iranian factions in Lebanon.

1987: U.S. Executive Order 12613 prohibits the import of Iranian products and oil into the United States; Iran signs a $5.5 million deal with Argentina to supply a new TRR core.

1988: Guided missile cruiser USS Vincennes shoots down Iran Air Flight 655 in the Strait of Hormuz, killing 290 passengers and crew; U.S. says that American forces mistakenly identified the civilian Airbus A300 as a hostile military aircraft, and provides restitution to the families of the victims; Iran accepts UN Resolution 598, calling for a cease-fire with Iraq, effectively ending the war; estimates of Iranians killed, including victims of Iraqi chemical weapon attacks, range from 180,000 to 300,000.

1989: Khomeini dies; former President Ali Khamenei (1939–) becomes supreme leader; Ali Akbar Hashemi Rafsanjani (1934–) is elected president.

1990: Iran signs a nuclear cooperation agreement with China.

1992: Iran and Russia sign an agreement on the sale of heavy-water reactors to Iran; U.S. Iran-Iraq Arms Nonproliferation Act imposes sanctions on foreign entities that provide Iran technology that could be used in the development of WMDs.

1993: Iran signs the Chemical Weapons Convention; it is ratified by parliament in 1997.

1995: Iran signs $800 million deal with Russia to complete the Bushehr nuclear power plant; U.S. Executive Order 12957 prohibits transactions related to the development of Iran’s oil industry; U.S. Executive Order 12959 prohibits re-exportation of goods or technology to, and investments in, Iran.

1996: U.S. Iran and Libya Sanctions Act (ILSA)—later known as Iran Sanctions Act (ISA)— imposes sanctions on foreign entities that invest in Iran’s energy sector.

1997: Reformist cleric Mohammed Khatami (1943–) is elected president; U.S. Executive Order 13059 clarifies Executive Orders 12957 and 12959 confirming that virtually all trade and investment activities with Iran by U.S. persons, wherever located, are prohibited.

1998: Khatami proposes a “dialogue among civilizations” in hopes of easing U.S.-Iranian tensions.

1999: Iran and Saudi Arabia support a Weapons of Mass Destruction-Free Zone in the Middle East.

2000: Secretary of State Madeline Albright says Washington bears some responsibility for turbulent U.S.-Iranian relations, citing support for shah’s repressive regime, backing for Saddam Hussein in the Iran-Iraq War, and role in the 1953 coup; U.S. lifts sanctions on non-oil products including carpets, pistachios, and caviar; U.S. Iran Nonproliferation Act sanctions foreign entities assisting Iran’s development of WMDs; reformists win a majority of seats in parliamentary elections.

2001: Al-Qaeda attacks World Trade Center in New York and Pentagon in Washington, DC, killing 3,000; United States leads invasion of Afghanistan; President George W. Bush says aim is “to disrupt the use of Afghanistan as a terrorist base of operations, and to attack the military capability of the Taliban regime”; U.S. Executive Order 13224 blocks assets of entities or individuals supporting terrorism.

2002: Bush accuses Iran, Iraq, and North Korea of pursuing weapons of mass destruction and labels the regimes an “axis of evil”; Mujahedeen Khalq opposition group reveals that Iran is secretly building two nuclear sites: a uranium enrichment facility in Natanz, and a heavy-water nuclear plant in Arak.

February 2003: Iran acknowledges Natanz and other facilities, and announces that it has extracted uranium from a newly discovered mine in Savand; Iran accepts modifications in NPT Subsidiary Arrangements, requiring Iran to notify IAEA of intentions to set up nuclear facilities; it is not ratified by parliament.

March 2003: United States leads invasion of Iraq; Bush says aims are “to disarm Iraq of weapons of mass destruction, to end Saddam Hussein’s support for terrorism, and to free the Iraqi people.”

May 2003: Swiss Ambassador to Iran Tim Guldimann delivers an Iranian offer to the United States, said to be backed by Khamenei and Khatami, proposing negotiations on a broad range of issues including nuclear safeguards, economic cooperation, coordination in Iraq, support for an Arab plan for peace with Israel, and halting weapons supplies to Palestinian groups; Bush administration ignores the proposal.

September 2003: Khatami says in a speech: “We don’t need atomic bombs, and based on our religious teaching, we will not pursue them. But at the same time, we want to be strong, and being strong means having knowledge and technology.”

October 2003: Iranian lawyer Shirin Ebadi (1947–) is awarded the Nobel Peace Prize “for her efforts for democracy and human rights”; Iran begins negotiations over its nuclear program with Britain, France, and Germany (EU3); in the Sa’dabad Declaration, Khatami agrees to suspend all enrichment activities, allow snap inspections by the IAEA, and sign the Additional Protocol of the Safeguards Agreement.

November 2003: Iran announces temporary suspension of its uranium enrichment program.

December 2003: Iran signs the Additional Protocol; it is not ratified by parliament.

2004:  Iran acknowledges covert program to acquire nuclear technology; announces plan to build a heavy-water nuclear reactor; Iran reveals production of hexafluoride gas used to enrich uranium, ignoring the IAEA’s demand for suspension of all enrichment activities; Iran and EU3 sign Paris Agreement, under which EU3 and Iran will negotiate on guarantees that Iran’s nuclear program is for peaceful purposes and on commitments on nuclear, technology, and economic cooperation.

February 2005: Iranian Minister of Defense Ali Shamkhani says in an interview with Iranian newspaper Sharq that acquiring a nuclear weapon is not in Iran’s national interest; Iran and Russia sign an agreement for Russia to supply the Bushehr nuclear facility with fuel and Iran to return the fuel rods to ensure enriched uranium is not used for production of nuclear weapons.

June 2005: U.S. Executive Order 13382 freezes assets of entities that support proliferators of WMDs; hardliner and former Tehran Mayor Mahmoud Ahmadinejad (1956–) is elected president.

August 2005: Khamenei issues a religious ruling (fatwa) forbidding the “production, stockpiling and use of nuclear weapons”; at United Nations, Ahmadinejad calls denial of Iran’s nuclear rights “nuclear apartheid”; Bush threatens Iran with military force over its nuclear program, saying “all options are on the table.”

October 2005: International controversy erupts over Ahmadinejad’s reported comment at a “World Without Zionism” conference in Tehran that Israel should be “wiped off the map.”

January 2006: Iran announces that it has achieved the capacity to extract uranium from ore; Iran breaks IAEA seals at the Natanz facility.

February 2006: IAEA refers Iran to the United Nations Security Council (UNSC) for noncompliance of the Safeguards Agreement after reporting inconclusive findings about Iran’s nuclear program.

April 2006: IAEA report says that Iran produced 3.6 percent enriched uranium but found no sign that Iran enriched uranium for military purposes.

May 2006: United States, Britain, and France draft a UN resolution that would force Iran to halt uranium enrichment activities, or face penalties and potential military action; China and Russia reject the resolution.

June 2006: P5+1 negotiating group is formed, consisting of the five permanent members of the UN Security Council (United States, Britain, France, Russia and China) and Germany; it offers Iran economic, political, and technological incentives if it addresses all IAEA concerns regarding its nuclear program.

July 2006: UNSC Resolution 1696 demands that Iran halt uranium enrichment activities within a month.

August 2006: Ahmadinejad inaugurates heavy-water nuclear plant in Arak; Iran rejects P5+1 proposals, citing condition that it suspend uranium enrichment.

September 2006: U.S. Iran Freedom Support Act appropriates $10 million to aid groups opposed to the Iranian government.

December 2006: UNSC Resolution 1737 is adopted after Iran fails to comply with Resolution 1696; It freezes assets of entities supporting Iran’s nuclear program, and bans export of nuclear-related materials and technology to Iran.

January 2007: Iranian state media reports that nuclear scientist Ardeshir Hosseinpour died of asphyxiation due to a gas leak in his apartment.

March 2007: UNSC Resolution 1747 expands the freeze on Iranian assets, bans arms sales to Iran, and asks global financial institutions not to enter commitments with the Iranian government.

April 2007: Ahmadinejad announces that Iran has achieved the capacity to produce nuclear fuel on an industrial scale; Iranian nuclear negotiator Ali Larijani says Iran has injected gas into 3,000 centrifuges.

August 2007: Iran and IAEA reach agreement for a work plan that specifies processes and a timeline to resolve outstanding issues regarding Iran’s Safeguards Agreement

November 2007: IAEA report states that Iran has “provided sufficient access to individuals and responded in a timely manner to questions” regarding its nuclear program; IAEA Director General Mohamed ElBaradei calls on Iran to suspend uranium enrichment activities and fully implement the Additional Protocol; Iran acknowledges that it acquired nuclear technology, including P-2 centrifuge blueprints, from A.Q. Khan network over the past two decades; U.S. National Intelligence Estimate states “We judge with high confidence that in Fall 2003, Tehran halted its nuclear weapons program.”

February 2008: IAEA report says Iran failed to disclose efforts to link uranium processing and explosives and to design missile warheads.

March 2008: UNSC Resolution 1803 demands that Iran halt uranium enrichment and heavy water-related activities, and urges states to limit financial transactions with Iran and cut ties with two Iranian banks.

June 2008: P5+1 announces a repackaged proposal based on the June 2006 offer.

July 2008: Under Secretary of State for Political Affairs William J. Burns participates in talks with Iranian negotiators in Geneva.

September 2008: UNSC Resolution 1835 reaffirms four previous UNSC resolutions on Iran.

March 2009: President Barack Obama, in a Nowruz message to Iran’s “people and leaders,” calls for an end to “old divisions”; Obama says: “The United States wants the Islamic Republic of Iran to take its rightful place in the community of nations.”

June 2009: Ahmadinejad is declared the winner in presidential election; reformist opponent Mir-Hossein Moussavi alleges election fraud; hundreds of thousands of “Green Movement” supporters hold demonstrations; months of disturbances result in an estimated seventy months deaths.

September 2009: Iran acknowledges to the IAEA the existence of the Fordo uranium enrichment facility near Qom.

October 2009: P5+1 announces the TRR fuel swap proposal, for low-enriched uranium to be shipped from Iran to Russia and then to France for further enrichment; fuel rods would be then sent to Iran for production of isotopes for medical use; Iran rejects fuel swap proposal.

November 2009: IAEA condemns Iran for developing the secret uraniaum enrichment site near Qom; Iran announces plans to establish ten additional enrichment sites.

January 2010: Iranian state media reports that a remote-controlled bomb explosion killed Masoud Ali-Mohammadi, a physics professor at Tehran University reportedly tied to Iran’s nuclear program.

February 2010: Ahmadinejad announces that Iran has produced 20 percent enriched uranium.

May 2010: Iran signs Tehran Declaration agreement with Turkey and Brazil calling for a TRR fuel swap; United States, Russia, and France reject agreement; U.S. Comprehensive Iran Sanctions, Accountability, and Divestment Act (CISADA) expands previous American punitive measures against foreign entities that invest in Iran’s oil industry, and sanctions human rights violators in Iran.

June 2010: UNSC Resolution 1929 demands that Iran comply with previous UNSC resolutions, and expands financial, military, and travel sanctions on Iran; security researchers identify Stuxnet 0.5 computer virus attacking Iranian targets.

August 2010: Iran holds ceremony marking the completion of the Bushehr nuclear plant; in 2011, officials announce that the plant has been connected to Iran’s national energy grid; EU bans trade related to Iranian natural gas production.

November 2010: Ahmadinejad announces that a cyber attack damaged centrifuges at an Iranian nuclear facility; experts believe that a Stuxnet attack struck Natanz; Iranian state media reports that separate bomb blasts in Tehran killed nuclear engineer Majid Shahriyari and injured nuclear scientist Fereydoun Abbasi-Dabani.

July 2011: Ahmadinejad welcomes a “road map” proposed by Russian Foreign Minister Sergei Lavrov that calls for eventual suspension of UN sanctions and limited enrichment activity in Iran; Iranian media report that gunmen assassinated nuclear scientist Dariush Rezaeinejad; Der Speigel reports that Mossad, Israel’s national intelligence agency, is behind the killing.

November 2011: Fars News Agency reports that a bomb explosion at an arms depot near Tehran killed seventeen members of the Iranian Revolutionary Guard Corps, including Major General Hassan Moqqadam, a key figure in Iran’s ballistic missile program; U.S. Executive Order 13590 imposes sanctions on entities supporting the development of Iran’s energy industry.

January 2012:  EU imposes an embargo on Iranian oil imports and freezes Iran’s central bank assets; Iranian media reports that an explosion in Tehran killed nuclear scientist Mostafa Ahmadi Roshan.

February 2012: Iran announces installation of Iranian-made nuclear fuel rods at TRR; NBC News, citing two anonymous senior U.S. officials, reports that Mossad is working with the Iranian opposition group Mujahedeen Khalq to assassinate Iranian nuclear scientists; U.S. Executive Order 13599 imposes sanctions on Iran’s financial institutions and certain individuals, as well as on property and interests held by the Iranian government.

March 2012: SWIFT international banking network bars electronic transactions by Iranian banks.

April 2012: U.S. Executive Order 13606 blocks property and entry into the United States of Iranians involved in human rights abuses by means of information and communications technology.

May 2012: U.S. Executive Order 13608 bans certain transactions with—and bars entry into the U.S. to—those who evade or violate U.S. sanctions on Iran or Syria; IAEA reports traces of 27 percent enriched uranium at the Fordo facility.

June 2012: New York Times reports that the Bush administration developed a covert program, Operation Olympic Games, aimed at sabotaging Iran’s nuclear program through cyber attacks; the paper says the Obama administration continued the program.

July 2012: U.S. Executive Order 13622 imposes new sanctions on Iranian energy and petrochemical sectors.

August 2012: U.S. Iran Threat Reduction & Syria Human Rights Act (ITRSHRA) broadens sanctions on foreign entities doing business with Iran’s energy, financial, and transportation sectors.

September 2012: Israeli Prime Minister Benjamin Netanyahu warns that Iran’s stockpile of enriched uranium could put it within reach of a nuclear weapon by mid-2013; hints at military attack if Iran fails to heed “red line.”

October 2012: U.S. Executive Order 13628 authorizes implementation of ITRSHRA, including sanctions on foreign subsidiaries of U.S. firms.

January 2013: Israeli Defense Minister Ehud Barak says “if worse comes to worst, there should be a readiness and an ability to launch a surgical operation that will delay [Iran’s nuclear weapons program] by a significant time frame.”

February 2013: Vice President Joe Biden offers direct talks on Iran’s nuclear program; Khamenei rejects the offer saying sanctions on Iran are a “gun held to its head.”

March 2013: Asked on Israeli television if the U.S. would attack Iran if diplomacy failed, Obama said “All options are on the table. The United States obviously has significant capabilities.”

April 2013: Iran announces it has activated a uranium processing plant and two uranium mines to expand Iran’s capacity to produce nuclear material.

May 2013: IAEA report finds that Iran has produced 324 kg of 20 percent enriched uranium;U.S. ends ban on sale of communications equipment and software to Iranians.

June 2013: Cleric Hassan Rowhani (1948–), former secretary of Iran’s Supreme National Security Council and lead nuclear negotiator, is elected president; U.S. Executive Order 13645 imposes sanctions on Iran’s automobile industry and on transactions in Iranian currency.