How Iran Transformed From Secular Monarchy To Shia Islamic Republic

The United States and Israel's latest unilateral declaration of war on Iranian cities has drawn attention to the reality that Iran is not just another state in West Asia. It is the political and religious centre of Shi'ism, one of the two major sects in Islam.

Today, 90-95 per cent of Iran's population identifies as Shia Muslim. It is the world's largest Shia-majority country. But Iran was not always organised as a Shia theocracy. Its religious identity evolved over centuries, shaped by empire, conquest, monarchy, revolution and political struggle.

To understand Iran's role in today's regional tensions, one must look at three turning points: the Muslim conquest of Persia in 651 CE, the Safavid decision in 1501 to impose Shi'ism as the state religion, and the Islamic Revolution of 1979.

Before Islam: Zoroastrian Persia

Before Islam arrived, the region we now call Iran was the heartland of ancient Persian empires. From around 1000 BCE until the Arab conquest in 651 CE, the dominant religion was Zoroastrianism.

Under the Achaemenid, Parthian and Sasanian empires, Zoroastrianism shaped political and social life. It centred on the worship of Ahura Mazda and the moral struggle between good and evil. Fire temples and priestly classes known as Magi played key roles.

Other faiths coexisted in Persian lands, including Judaism and Christianity. The empire was religiously diverse, even if Zoroastrianism held primacy.

The Muslim Conquest And The Sunni-Shia Divide

Islam entered Iran through the Arab conquest in 651 CE. Over the next centuries, most Iranians converted to Islam.

The split between Sunni and Shia Islam began earlier, after the death of the Prophet Muhammad in 632 CE. The dispute was over leadership. One group supported Abu Bakr as caliph. Another believed leadership belonged to Ali, the Prophet's cousin and son-in-law.

The killing of Husayn, Ali's son, at Karbala in 680 CE deepened the divide. His death became a major element to Shia identity. Mourning rituals during Ashura still commemorate this event.

For centuries, Iran was largely Sunni. That changed in the 16th century.

The Safavid Turning Point

In 1501, Shah Ismail I founded the Safavid dynasty and declared Twelver Shiism the state religion. This decision transformed Iran permanently.

The Safavids were originally Sunni with Sufi roots. Their shift to Shiism was political. It distinguished Iran from the rival Sunni Ottoman Empire and helped centralise authority.

Clerics were brought from Arab regions of present-day Lebanon and Iraq to build a Shia religious establishment. Over time, Iranian Shia scholars emerged and gained influence.

Under figures like Mohammad Baqir Majlisi in the 17th century, Shia jurisprudence became central to governance. Rituals like Ashura were promoted. Shrines in Mashhad and Qom gained importance. Alternative religious expressions, especially Sufi movements, were restricted.

From this period onward, Iran's identity became firmly tied to Shia Islam.

The Constitutional Era

In 1906, Iran experienced a Constitutional Revolution. A parliament was introduced. The monarchy's powers were limited. While Shia Islam remained the state religion, minorities such as Jews, Christians and Zoroastrians received legal recognition.

Western ideas such as nationalism and constitutionalism influenced reformers. This was the beginning of a modern Iranian nation-state.

The Pahlavi Dynasty

From 1925 to 1979, Iran was ruled by the Pahlavi dynasty.

Reza Shah Pahlavi reduced the power of the clergy, centralised authority and introduced legal reforms influenced by Europe. He banned the hijab in 1936 and promoted Western dress. Religious courts lost control over education and law.

His son, Mohammad Reza Shah, continued these policies. The 1963 White Revolution introduced land reforms and women's suffrage. The state, not the clergy, controlled religious endowments.

Iran during this period can be described as hybrid-secular. Shia Islam remained the official religion under the 1906 constitution, but religious authorities were marginalised politically.

The Shah also promoted Iran's pre-Islamic Persian heritage, celebrating figures such as Cyrus the Great. This reportedly angered conservative religious groups, who saw it as cultural Westernisation.

While cities modernised, much of rural society remained deeply religious. Tensions between secular reforms and religious identity grew.

The Islamic Revolution Of 1979

Resentment against the Shah's rule, economic inequality, and perceptions of Western interference led to mass protests in 1978-79.

Ayatollah Ruhollah Khomeini, a cleric in exile, returned from France as the revolution's leader. He advocated governance based on Islamic principles.

After the Shah fled, the Islamic Republic of Iran was established. The new constitution enshrined Twelver Shiism as the state religion and introduced the concept of Velayat-e Faqih, Guardianship of the Islamic Jurist. The Supreme Leader, a senior cleric, became the highest authority.

Sharia law shaped legal and social life. Clergy dominated key institutions. Religious codes on dress and behaviour were enforced. Recognised minorities retained limited rights, while unrecognised groups such as the Baha'is faced persecution.

Iran had shifted from a monarchy with secular reforms to a modern theocracy.

Iran And The “Shia Crescent”

Shia Muslims make up about 15 per cent of the global Muslim population. Yet they are concentrated in a corridor stretching from Lebanon through Iraq to Iran.

This network is often called the “Shia crescent.” Groups such as Hezbollah in Lebanon, Shia-majority Iraq, and the Houthis in Yemen have varying degrees of connection with Tehran.

Iran presents itself as a defender of Shia communities beyond its borders. This shapes its foreign policy and contributes to regional tensions, especially with Sunni-led states and with Israel.

Internal Dissent

Despite its official religious identity, Iranian society is not uniform.

Surveys such as one conducted by GAMAAN in 2020 suggest that levels of religious identification may be changing, especially in urban areas. Protest movements in recent years, including demonstrations following the death of Mahsa Amini in 2022, have challenged religious restrictions and state authority.

Iran recognises Sunnis, Christians, Jews and Zoroastrians as minorities, though their political power is limited. Religious authority remains concentrated in clerical institutions, especially in Qom.