1,400 years ago, during the seventh century, there was a schism among Muslims over who would succeed as leader of the faithful, and that schism led to a civil war. The two sides became known as Sunni and Shia, and they hated one another, a people divided, ever since. This ancient sectarian hatred, simmering just beneath the surface for centuries, explains the Sunni-Shia violence today in places such as Syria and Iraq, as well as the worsening tension between Saudi Arabia, which is officially Sunni, and Iran, which is officially Shia.

But this narrative could not be more wrong. Yes, it is the case that a seventh-century succession dispute led to Islam’s schism between Sunni and Shia. But that is quite literally ancient history. Today’s divide between Sunni and Shia isn’t primarily about religion, and it’s not ancient: It’s quite recent, and much of it is driven by politics, not theology.

Sunni-Shia sectarianism is indeed tearing apart the Middle East but is largely driven by the very modern and very political rivalry between Iran and Saudi Arabia. They have sought to fight one another on Sunni-Shia lines not out of religious hatred but rather because they see sectarianism as a tool they can use — thus making that religious division much more violent and fraught.

Marc Lynch, a George Washington based University professor, and Middle East scholar, wrote a lengthy piece on this week’s uptick in Iran and Saudi Arabia’s regional cold war, which is playing out largely along Sunni-Shia lines, titled “Why Saudi Arabia escalated the Middle East’s sectarian conflict.”

The article was widely circulated by Middle East experts as authoritative and insightful. Some of the reasons Lynch discusses include a desire to distract from Saudi foreign policy failures elsewhere, a fear that the United States is softening on Iran, and an effort to appease hard-line Islamist elements at home.

Noticeably absent from Lynch’s list of factors: that Saudi Arabia hates the Shia due to theological disagreements or seventh-century succession disputes.

That’s not a mistake. No one who seriously studies the Middle East considers Sunni-Shia sectarianism to be a primarily religious issue. Rather, it’s a primarily political issue, which has manifested along lines that just so happen to line up with religious demographics that were historically much calmer and more peaceful.

Al Jazeera’s renowned Mehdi Hasan put together a very nice video debunking the myth that Sunni-Shia sectarianism is all about ancient religious hatreds and explaining how modern-day power politics, beginning in 1979, is actually driving much of the sectarianism.

It will be false to claim that there was never any communal Sunni-Shia violence before 1979. Nor is this to say that Iran and Saudi Arabia were the first or only countries to cynically exploit Sunni-Shia lines for political gain: Saddam Hussein did it too, and so have some Islamist groups. I want to be careful not to overstate this and give the impression that Sunni-Shia lines were completely and always peaceful before 1979, nor to overstate the role Saudi Arabia and Iran played in turning Sunni and Shia against one another.

But it is very much the case that Sunni and Shia differences have only quite recently become such a defining issue for the Middle East, and certainly that they have become so violent.

And it is very much the case that the Sunni-Shia divide has widened for mostly political reasons, due to the deliberate and cynical manipulations of Middle Eastern leaders, and not because Middle Easterners suddenly woke up one day and remembered that they hated one another over a seventh-century succession dispute.

For much of the Middle East’s modern history, the Sunni-Shia divide was just not that important for the region’s politics. In the 1950s and ’60s, the leading political movement in the Middle East was Arab nationalism, for which Sunni-Shia distinctions were largely irrelevant. And in the 1980s, for example, the biggest conflict in the Middle East was between two Shia-majority countries — Iran and Iraq — with Sunni powers backing Iraq. Shia Iran has been a major supporter of Sunni Hamas (though that has abated somewhat recently). And so on.

Things first started to change in 2003, when the United States led the invasion of Iraq to topple Saddam Hussein.

Obviously, Iraqis were aware of Sunnism and Shiism before 2003, and those distinctions were not totally irrelevant to Iraqi life. But for much of Iraq’s modern history, Sunni and Shia lived peacefully side by side in mixed neighborhoods and frequently intermarried. For decades after decolonization, Iraqis defined themselves first by their ethnicity as Arabs or Kurds or by their nationality as Iraqis. Religious distinctions were just not as important.

“The roots of the sectarian conflict aren’t that deep in Iraq,” Fanar Haddad, a scholar of Iraqi history, once told my colleague Zack Beauchamp. “Sectarian identity for most of the 20th century was not particularly relevant in political terms.”

The change came because of regional power politics, which the 2003 US-led invasion upset. Saddam was hostile to both Iran and Saudi Arabia (despite Saudi support for his 1980s war against Iran), and those two countries saw him as a wild-eyed threat. He held the Middle East in a precarious sort of balance among these three regional military powers.

It is true that Saudi Arabia is an officially Sunni theocracy and that Iran is an officially Shia theocracy.

But they don’t hate one another because of religious differences, and in fact both countries have in the past defined themselves as representing all Muslims. Yet they can’t both be the true representative of all Muslims, and that’s the thing to understand here: The two countries have mutually exclusive claims to leadership of the Muslim world. The sectarian difference is largely coincidental.

This conflict began in 1979 when the Iranian revolution turned secular Iran into a hard-line Shia theocracy

After Iran’s 1979 Islamic Revolution toppled the pro-Western shah, the new Islamic Republic established an aggressive foreign policy of exporting the Iranian revolution, attempting to foment Iran-style theocratic uprisings around the Middle East. That was a threat to Saudi Arabia’s heavy influence in the Middle East, and perhaps to the Saudi monarchy itself.

“The fall of the shah and the establishment of the militant Islamic Republic of [founding leader] Ruhollah Khomeini came as a particularly rude shock to the Saudi leadership,” University of Virginia’s William Quandt writes. It “brought to power a man who had explicitly argued that Islam and hereditary kingship were incompatible, a threatening message, to say the least, in [the Saudi capital of] Riyadh.”

It’s important to understand that the Saudi monarchy is deeply insecure: It knows that its hold on power is tenuous, and its claim to legitimacy comes largely from religion. The Islamic Republic of Iran, merely by existing, challenges this legitimacy — not because it is Shia but because its theocratic revolution was popular and anti-monarchist. The Saudis saw this as a declaration of war against their very monarchy and a serious threat to their rule, and indeed in some ways it was.

This rivalry has been with the Middle East ever since 1979: with the Saudis supporting Saddam’s war against Iran and with the two countries supporting different sides in Lebanon’s civil war, for example. But it did not come to define the Middle East until the 2003 invasion of Iraq, and especially with the 2011 Arab Spring.

In 2011, when the Arab Spring began upending governments across the Middle East, both Saudi Arabia and Iran again tried to fill the vacuums, and that often meant supporting violence. It also meant deliberately amping up Sunni-Shia sectarianism to serve their interests.

In weak states, Iran and Saudi Arabia have tried to position themselves as the patrons of their respective religious clans to assert influence, and they have ginned up sectarianism to promote fear of the other side. A sectarianism is just a tool. But that sectarianism has become a reality as Middle Eastern militias and political parties line up along sectarian lines and commit violence along those lines.

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