The story, as told, usually goes something like this: 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.

Debunking the "ancient hatreds" myth

Marc Lynch, a George Washington 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 piece 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 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 we're seeing right now:

#RealityCheck: The myth of a Sunni-Shia war. @mehdirhasan on how the sectarian narrative isn’t backed by the facts https://t.co/xpaa1rfA4d — UpFront (@AJUpFront) January 4, 2016

Hasan's video is especially worth watching for his illustration of just how modern the Sunni-Shia political division really is.

Now here come the caveats: This is not to say 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.

"As usual, religion is a mere instrument of state ambitions"

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.

If the Sunni-Shia conflict isn't about religion, where did it come from?

Things first began 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 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.

"Sectarian identity for most of the 20th century was not particularly relevant in political terms"

When the US toppled Saddam, it removed that balance, and opened a vacuum in Iraq that both Saudi Arabia and Iran attempted to fill so as to counter one another. Because Iraq is mostly Shia (Saddam had been Sunni), Iran tried to exploit sectarianism to its advantage, backing hard-line Shia groups that would promote Iranian interests and oppose Sunni powers like Saudi Arabia. It also put pressure on the new Iraqi government to serve Iranian interests, which came to be equated with Shia interests.

In this way, political maneuvering in post-Saddam Iraq that was not primarily about religion came to be expressed as about religion. It helped deepen the Sunni-Shia split there so severely that this divide today defines Iraq.

That's just the story of Iraq, but the same story is playing out across the Middle East, and a lot of it has to do with that same Saudi-Iran rivalry.

Where today's Sunni-Shia conflict really comes from: Iran and Saudi Arabia

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. My colleague Zack Beauchamp explains:

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. 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.

You can see the same thing unfolding in Syria. The violence at first had little to do with religion: It was about the Syrian people versus a tyrannical government. But the Syrian government is allied with Iran, which means it is hostile to Saudi Arabia, so the Saudis see it as their enemy. The Saudis and other Sunni Gulf states armed Syrian rebels who are Sunni hard-liners, knowing the rebels' anti-Shia views made them more hostile to Iran and more loyal to Saudi interests.

Iran used much the same strategy, portraying the Syrian war as a genocidal campaign against Shia. This helped Tehran attract Shia militias from Iraq and Lebanon that would fight for Iranian interests. Making the Syrian civil war as sectarian as possible also ensures that the Syrian government, which is Shia, will remain loyal to Iran.

French Ambassador to the US Gérard Araud put it pretty well when he said, commenting on Hasan's video, "As usual, religion is a mere instrument of state ambitions."

The story of Baghdad, and the terrible logic of sectarianism

Sunni-Shia hatred in the Middle East may be new, and it may be artificial. But over the past decade, it has nonetheless become very real. Sectarian fear, distrust, and violence now exists at a grassroots level. The hostility runs so deeply now that although Sunni-Shia tension is not ancient, it might as well be.

Tribalism — that is, the tendency to side with your own group, however defined, especially in times of conflict — has its own internal logic and momentum that often has little or nothing to do with the demographics through which it manifests. But once a society divides along tribal lines — whether they are religious or racial or ethnic — those lines become experienced as real.

Consider Rwanda: Before colonialism, the line between Hutu and Tutsi was mostly a class distinction, and often a blurry one . But about a century ago, Belgian colonists hardened the distinction, pushing the idea that Hutus and Tutsis were completely distinct ethnic groups and entrenching Tutsis as dominant over Hutus. As such, after colonialism, political grievances fell along this ethnic line. Even though the ethnic distinction was arguably in part a modern colonial invention, Rwandans began to treat it as real, which helped lead to one of the worst genocides in modern history.

Consider also the city of Baghdad. For much of its history, Sunni and Shia lived generally peacefully, side by side in mixed neighborhoods.

But when the US toppled Saddam and disbanded the Iraqi army, it opened a dangerous security vacuum. Lawlessness and street justice prevailed. Communities that happened to be Sunni or Shia formed self-defense militias, first to protect themselves, then to exact revenge killings. Sunni families and Shia families came to see one another as threats, and the militias committed massacres to drive out the other side. In just two years, Baghdad's once-mixed neighborhoods were starkly divided by religion.

The story of Baghdad is important not because it's necessary to blame America for everything but because this was in some ways the start of today's Sunni-Shia region-wide war, and it shows how that conflict is not really primarily about religion.

Rather, it is a story of how insecurity and fear can lead a once-unified people to divide themselves along some tribal line, which then hardens into hatred and violence. And it shows how people will split along whichever lines are most readily available, or whichever lines happen to line up with the politics of the moment. In that case, it was religion. But there's little to this story that is in itself religious, much less ancient.