Violence against women is often cast in the history books as a side effect of war, the inevitable outcome when empires clash, cities fall and triumphant armies let loose on helpless civilians. But as a flurry of recent reports note, there's nothing inadvertent about the Islamic State's systematic enslavement and abuse of hundreds of captured women -- rather, it's embedded in the group's worldview and strategic operations.

The Middle East Media Research Institute (MEMRI), which monitors Islamist militant online activity, this week published a comprehensive analysis of the jihadists' practice of sexual slavery, drawn from Islamic State communiques as well as the social media accounts of its members and supporters. It followed a searing expose by New York Times reporter Rukmini Callimachi detailing how the Islamic State has "enshrined" a "theology of rape."

There is a well-organized system in place for the buying and selling of female slaves

Reports of the Islamic State capturing women and often forcing them to serve as the jihadists' enslaved concubines began piling up last autumn after the militants overran villages in the shadow of Iraq's Sinjar mountain. The region is home to the Yazidi sect, a largely Kurdish-speaking minority whose faith predates the advent of Islam and is considered apostate by fundamentalists.

Some of the Yazidis who couldn't escape, particularly able-bodied men, were summarily executed. Others, particularly young women, were rounded up and carried away.

More than 5,000 Yazidi women were captured last year, and an estimated 3,144 are still being held by the militants, according to the Times. The testimony of those who eventually escaped -- or had their freedom bought by relatives and friends -- has provided a shocking window into the world of the Islamic State.

Callimachi charted the elaborate system the Islamic State put in place to transport, house and trade female slaves. It involves buses seized from the Iraqi government, large warehouses and office buildings as holding pens and a bureaucracy of courts and notaries that presides over contracts and deeds of sale.

Younger Yazidi girls fetch higher prices in the Islamic State slave markets. According to some accounts, those higher up in the organization's command structure get first choice. But it's clear the trade comprises a real wing of the Islamic State's internal economy.

"The girls get peddled like barrels of petrol," Zainab Bangura, the United Nations' special representative on sexual violence and conflict, said in an interview with the Sydney Morning Herald. "One girl can be sold and bought by five or six different men. Sometimes these fighters sell the girls back to their families for thousands of dollars of ransom."

Islamic State jihadists invoke religion to justify rape and slavery

The barbaric crimes committed against the captured Yazidi women -- which, according to one account, included burning alive a woman who refused to submit to a particularly extreme sex act -- are sometimes explained away using religion.

As MEMRI documents, there's substantial official literature on the rights and wrongs of slavery within the Islamic State. Late last year, the organization's "Research and Fatwa Department" put out a 27-point-pamphlet on how to treat one's female slave.

It sanctioned the capture and "immediate" rape of "unbelieving" women, especially virgins, as well as young girls who have not reached puberty. But it forbade the theft of another comrade's slave and advised militants not to strike their slaves on the face. Given that the woman is supposedly the jihadist's property, what the jihadist chooses to do can't be considered rape.

An article in the fourth issue of the Islamic State's semi-official magazine, Dabiq, outlined the religious justification for enslaving the Yazidis, as opposed to the Christians living in the midst of the militants, some of whom have been allowed to carry on with their daily lives following the payment of a religious tax. MEMRI quotes the key passage:

"Prior to the taking of Sinjar, Shariah students in the Islamic State were tasked to research the Yazidis to determine if they should be treated as an originally mushrik [polytheists] group or one that originated as Muslims and then apostatized, due to many of the related Islamic rulings that would apply to the group, its individuals, and their families... The apparent origin of the religion is found in the Magianism of Ancient Persia... Accordingly, the Islamic state dealt with this group as the majority of fuqaha [scholars] have indicated how mushrikin should be dealt with. Unlike the Jews and Christians, there was no room for jizyah payment. Also, their women could be enslaved unlike female apostates who the majority of the fuqaha say cannot be enslaved and can only be given an ultimatum to repent, or face the sword."

Callimachi's chilling story begins with an account of an Islamic State fighter lecturing a preteen girl he is about to rape on why the act was not a sin, binding and gagging her, and then, when the hideous deed was done, kneeling in prayer.

A blog post published by Israfil Yilmaz, a Dutch Islamic State fighter, and cited by MEMRI, makes the cringe-worthy argument that the jihadists' enslavement of these women has less to do with sex than with the Islamic State's historic mission to return the world to the days of the original caliphate. Many other militants deploy this reasoning as well on social media.

"People [who] think that having a concubine for sexual pleasure only have a very simple mindset about this matter. And yes [Yilmaz's wife] agrees (maybe she doubts I'll ever own one hahaha). The biggest and best thing of having concubines is introducing them to Islam in an Islamic environment - showing them and teaching them the religion. Many of the concubines/slaves of the Companions of the Prophet (PBUH) became Muslim and some even [became] big commanders and leaders in Islamic history and this is if you ask me the true essence of having slaves/concubines."

In the Times story, the girl told Callimachi: "He told me that according to Islam he is allowed to rape an unbeliever. He said that by raping me, he is drawing closer to God. I kept telling him it hurts — please stop."

In a Dabiq article published in May, an apparently female Islamic State jihadist condemned fellow Islamic State supporters who had initially denied that the organization was enslaving and raping women.

"The supporters started denying the matter as if the soldiers of the Khilafah had committed a mistake or evil," wrote Umm Summayyah Al-Muhajirah. She went on: "Indeed when slavery befalls a people, they have left Allah's favor," and she claimed it was hypocritical of people in the West to condemn the treatment of forced concubines, given their tolerance for prostitution.

The jihadist critics of the Islamic State's practices

The MEMRI report details internal disagreements over the capture of Muslim women and their treatment as slaves. Some believe it's acceptable to seize Shiite women, whom they claim are apostate, and whose husbands, fathers and sons are part of armies and militias fighting the Islamic State.

The report also cites the opposition of Jabhat al-Nusra, an Islamist group fighting in Syria that remains al-Qaeda's de facto proxy in the conflict. One al-Qaeda ideologue argues that, while it's theologically permissible to take female slaves, the current environment of guerrilla warfare makes it "impossible to regulate" and "would lead to actual abuses" -- as if the practice of female slavery isn't enough of an abuse already.

Another Salafist cleric cited by MEMRI is more scathing, saying the Islamic State's garish practices have led to "ramifications and consequences," including Yazidi and Kurdish militia reprisals on Sunnis. "Who is responsible?" asks Abu Qatada Al-Falastini, and then gestures to the Islamic State leader Abu Bakr al-Baghdadi: "The criminal Baghdadi and his group."

The captured women, and those who escaped, face horror and trauma

However the Islamic State chooses to represent their behavior, there are now thousands of women who have endured and seen monstrous acts. The U.N.'s Bangura is one of the more outspoken chroniclers of their plight, as WorldViews discussed in a post earlier this year:

"It was painful for me. The countries I have worked on include Bosnia, Congo, South Sudan, Somalia and Central African Republic," says Bangura, a former foreign minister of Sierra Leone who is no stranger to conflicts. "I never saw anything like this. I cannot understand such inhumanity. I was sick, I couldn't understand."