Iran is an ancient nation that lies in central Asia. Officially the Islamic Republic of Iran since 1979, its capital is Tehran. Iran is the second largest nation in the Middle East, and home to a significant amount of the world's oil, although its relations with the United States have been strained since the Islamic Revolution. Unlike most other Middle Eastern nations, the people of Iran are overwhelmingly Shi'a Muslim.
The history of Iran stretches back far into antiquity, dating to before the time of the Persian Empire. Alexander the Great conquered what is now Iran during his march to India, and that empire gave rise to the Parthian Empire, which frequently came into conflict with the Romans.
Modern Iran dates to 1921, when Reza Khan became Shah. During World War II, Iran was occupied by British and Soviet forces, and Reza Khan abdicated in favor of his son, Mohammad Reza Pahlavi. In 1951, Mohammad Mosaddegh was elected Prime Minister and nationalized the oil companies in Iran. Two years later, he was deposed by a CIA-led coup, and the Shah became increasingly autocratic.
By 1978, demonstrations against the Shah led to the Islamic Revolution, led by Ayatollah Khomeini. During the Revolution, American hostages were held for 444 days, leading to a rupture in relations with the United States that has lasted well into the 21st century. Continuing sanctions against the Iranian economy have hurt that nation, leading to a massive devaluation of its currency.