America's air strikes in Iraq aren't just about protecting Americans in the Kurdish capital of Erbil. "In recent days, Yazidi women, men, and children from the area of Sinjar have fled for their lives," President Obama said when announcing the airstrikes. "And thousands — perhaps tens of thousands — are now hiding high up on [a] mountain, with little but the clothes on their backs."

Obama explained the US is going to help them, with humanitarian airdrops and maybe even military strikes. "I've, therefore, authorized targeted airstrikes, if necessary, to help forces in Iraq as they fight to break the siege of Mount Sinjar and protect the civilians trapped there."

You may find yourself asking, then, who are the Yazidis? What do they believe? Why has the Islamic State (ISIS) trapped so many of them on a mountain without food and water? Why is the US trying to save them? Here are some answers.

The Yazidis (or Yezidis) are a ethno-religious minority concentrated largely in northern Iraq

The Yazidi or Yezidi — the two terms are used interchangeably — live principally in northern Iraq, in north-central Ninevah province and northeastern Iraqi Kurdistan. They've been in the region for about a thousand years. There are about 600,000 Yazidis worldwide, but mostly in Iraq. Estimates vary, but the Iraqi Yazidi population is thought to be somewhere between 400,000 and 500,000. That's split about evenly between Ninevah province and Kurdistan. Here's a map of Iraq, with Ninevah in the north spelled "Ninewah" and Iraqi Kurdistan's three formal provinces (Dohuk, Erbil, and Sulaymaniyah) nearby:

Ethnically, Yazidis are often identified as Kurds, the minority group that semi-autonomously governs a chunk of northeastern Iraq (most other Iraqis are ethnically Arab). Most Yazidis do consider themselves Kurds, according to Sebastian Maisel, a professor at Grand Valley State University who has conducted extensive fieldwork among Yazidis.

This is just one example of the long history of Yazidi persecution

But Iraq's Ba'athist government disagreed. Beginning around 1975, they labeled them an Arab offshoot, according to Maisel, in order to "distance them from the Kurdish population." The Ba'athist government decreed that Yazidis were descendants of Yazid bin Mu'awiya, the ancient caliph whom Shia Muslims remember ruefully as the murderer of the (in their view) rightful Caliph Husayn bin'Ali after Muhammed's death. This would make the Yazidis ethnically Arab — it would also alienate them from Shia Muslims, who are the Iraqi majority, and perhaps make Yazidis more reliant on the Sunni Ba'athist government.

The goal, according to Maisel, was to separate the Yazidis from the Kurds, who wanted political autonomy, and make them loyal to Arab Iraq. But it did this in a truly heavy-handed and brutal way. During the '70s and '80s, Saddam Hussein forcefully relocated Yazidis from their traditional home near the Sinjar mountains to cinderblock villages in poorly-resourced areas, gave them Arabic names, and forced them to speak Arabic and not Kurdish.

This is just one example of the long history of Yazidi persecution — which has often stemmed from a misunderstanding of their religion.

Yazidi religion is deeply persecuted around the Middle East because it is misunderstood as Satanism

Yazidis' religion and social structure sets them apart from the rest of Iraq's Kurds, who are mostly Sunni Muslims. Yazidi theology has many influences, one of which includes some resemblances to the Abrahamic fable of Satan. That is often widely misunderstood in the Middle East as worshipping Satan (it is absolutely not). According to Maisel, this misunderstanding of their theology is the "root cause" of Yazidi persecution throughout the centuries.

many of the Yazidis' neighbors don't understand the crucial difference between this story and the Satan myth

Yazidi religion holds that God governs the world through seven angels, the leader of whom is named Malak Tawous. Malak Tawous was the only angel to disobey God's command to bow down to humanity — that is the faint similarity between him and the Abrahamic story of Satan. However, in Yazidi theology, God forgave the disobedience. He saw it as a sign of devotion, and elevated Malak Tawous to the head of the angelic order.

But many of the Yazidis' neighbors don't understand the crucial difference between their story and the Satan myth.

"You might see that there's this resemblance, and if you don't understand that God forgave the angel, then you can say that they worship what we call the devil," Maisel says. "But they don't even have a hell. There's no concept of heaven and hell."

This misunderstanding has led to centuries of persecution, right up through ISIS's attempts to slaughter the group today. Those attempts are also premised on accusing the Yazidi of devil worship. A traditional Yazidi hymn recalls 72 attempts to exterminate their people. According to Maisel, this includes attempts by groups as diverse as "the Ottomans, Arabs, Sunnis, Kurds, Turks, Ba‘thists, and even the British." Throughout the Middle East, Maisel says, Yazidis are "at the bottom of the social hierarchy."

The much-derided Yazidi "caste system" is actually about religious duties

Yazidis also have some distinct social norms around how communities are organized. It's often referred to as a caste system, but Maisel thinks that's wrong. "We should not think of it as a caste system in the way we think of it in India. It has nothing to do with privileges or wealth," he says.

Instead, it's about who's responsible for religious duties — and about marriage. Every Yazidi is born either into a clergy family or a layman family, the two major social groups. Among the clergy families, there are two sub-sets: the sheikhs and the pirs (pronounced "peers.") Each has its own set of religious responsibilities. Sheikhs, for instance, preside over most major holidays, whereas pirs take the lead on life cycle events like birth.

The laymen families in turn provide the clergy families with financial assistance. "Each layman has to be associated with a sheikh and a pir," Maisel says, so they can all help each other. Intermarriage between the three groups, though, is forbidden.

The Iraq War was a boon to the Yazidis — until the rise of al-Qaeda in Iraq

After Saddam's awful treatment of the Yazidis and Kurds, both groups largely welcomed the American-led invasion in 2003. The Yazidis were able to move out of the villages Saddam had forced them into and "reestablish themselves as a religious community," as Maisel puts it.

That ability to resettle came "mainly as a result of the diaspora community [which] provided financial support to those living in Iraq." There are a number of Yazidis in the diaspora in the West, mostly in Europe, though there are some in the United States, including a large community in Lincoln, Nebraska.

During the war's early stages, the Yazidis — even those living in Sinjar, in the mostly-Sunni Ninevah province — managed to avoid the fighting. The territory was, according to Maisel, "widely recognized by the traditional Arab Sunni population as Yazidi territory."

But the rise in the mid-2000s of al-Qaeda in Iraq, the predecessor group to ISIS, was a disaster for the Yazidis.

"Al-Qaeda started to single out religious minorities and pushed for sectarian civil war," Maisel said. "You have this terrible event in 2007 where [al-Qaeda] carried out this massive suicide bombing in collective villages south of the Sinjar mountains where they killed 500 Yazidis. It's known as the deadliest attack of the Iraq war."

Al-Qaeda in Iraq had linked their own hyper-violent ideology to the preexisting suspicion of Yazidis as devil worshippers. That led to a wave of anti-Yazidi violence. The violence subsided after American troops and Iraqi Sunni militias joined forces to dismantle al-Qaeda in Iraq around 2007. But the violence rose again this summer as ISIS invaded from Syria and seized much of northern Iraq, bringing persecution of the Yazidis with them.

The ISIS siege is an imminent threat of Yazidi genocide

ISIS controls territory in Syria as well as Iraq, and its rise in Syria had driven a number of Syrian Kurds and Yazidis into Iraq as refugees. That Iraqi safe haven, however, was shattered when ISIS began its offensive on Iraqi Kurdistan in early August. ISIS captured Sinjar early in that offensive and targeted Yazidi civilians. Half of Iraq's enormous Yazidi population was forced to flee.

"For centuries," according to Maisel, Yazidis had hid from threats like ISIS in the mountains. That's why somewhere between 10,000 and 40,000 Yazidis fled to Mount Sinjar. However, in order to get out of range of ISIS's guns, they were forced into remote territory, away from any food and water. The Yazidi families are still stuck there, slowly starving to death. The United Nations and United States have both warned that these are the conditions for imminent acts of genocide.

That is why President Obama authorized military strikes on the ISIS forces that have besieged Mount Sinjar. He also sent the US military to airdrop emergency humanitarian supplies over the mountain, but that can only work so long. The siege has to be broken. But by whom?

The Kurdish military forces, known as peshmerga, are their best chance. Historically, the Yazidis have had a complicated relationship with the Kurdish authorities. "They wanted the protection of the Kurds to a degree," Maisel says, but "they weren't really thrilled about how the Kurdish government approached this, because the Kurdish government imposed their rule on the Yazidis."

Today, however, Maisel thinks the Kurds want to help break the siege. "Attempts were made to bring the Sinjar mountains back into the Kurdish provinces," he says, "and that's why there is so much Kurdish support for the Yazidis — because they see the Yazidis as part of their community."

the Yazidi community in Iraq is being torn apart

Obama's airstrikes, then, would have to be a supplement to any Kurdish military push in order to save the Yazidis. ISIS controls all of the access roads into Sinjar, and the US could help provide aerial cover during Kurdish fighting on the open roads. The US will attempt to repel ISIS's recent push into Kurdistan proper, where the rest of the Yazidis are taking refuge.

Whether that plan will work or not has yet to be seen. In the meantime, however, one thing is clear: the Yazidi community in Iraq is under one of the most dire threats it has faced in centuries of persecution.