Public beheadings like those of American journalists Steven Joel Sotloff and James Foley are part of ISIS' sophisticated video and social media strategy meant to sow terror in the Western world, U.S. officials and scholars say. But the Islamist extremists have larger goals than spreading fear with barbaric violence, they say, forcing Western governments to ask: What does ISIS really want?
To restore the caliphate
ISIS' stated goal is to restore the "caliphate" — an Islamic state under the rule of a community of religious scholars guided by a supreme leader, the caliph or khalifah, which is generally taken to mean the successor to the Prophet Muhammad.
But what ISIS means by a "caliphate" is very different from what history tells us about Islamic rulers of previous centuries, scholars say. The Abbasid Caliphate, which began in the 8th century A.D., fostered progressive achievements in science and philosophy and is remembered in history as the Golden Age of Islam. As early as the 10th century, Baghdad, the capital of the caliphate, was "the intellectual center of the world," Gaston Wiet, the French Middle East scholar wrote in his landmark history, "Baghdad: Metropolis of the Abbasid Caliphate."
ISIS, by contrast, puts forth a "deviant and pathological" interpretation of Islam at odds with the philosophies of the historical caliphs, said Leila Hudson, an associate professor at the School of Middle Eastern and North African Studies at the University of Arizona.
"Islam is a religion with more than a billion adherents, the vast majority of whom are horrified at this extremism," Hudson told NBC News on Monday.
In June, ISIS published a manifesto (PDF) purporting to trace the lineage of its leader, Abu Bakr al-Baghdadi, directly back to the prophet to establish his claim to be caliph. Its voracious expansionist aims are encapsulated in this declaration: "The legality of all emirates, groups, states and organizations becomes null by the expansion of the khilafah's authority and arrival of its troops to their areas."
ISIS is only one of the commonly used abbreviations for al-Baghdadi's organization, and you can keep track of his goals by the transformations in what the group calls itself.
Before it began to explicitly move away from al-Qaeda, it was known simply as the Islamic State of Iraq. In the past year or so, it adopted a name that could be translated variously as the Islamic State of Iraq and the Levant (ISIL), the Islamic State of Iraq and al-Sham or the Islamic State of Iraq and Syria (both shorthanded as ISIS). "Levant" linguistically suggests a broader territory than simply Iraq and Syria, also generally encompassing Jordan, Lebanon, Israel and the Palestinian territories, and "ISIL" is the name the Obama administration continues to use.
In June, when it declared al-Baghdadi to be a descendant of Muhammad and the rightful caliph, the group dropped all pretense of geographic boundaries, calling itself simply the Islamic State (IS), aiming to take in "every Muslim believer," according to its manifesto.
Already, "there's evidence of ISIS moving into Lebanon, and people in Jordan are very worried about ISIS," Hudson said. "Part of the context for the Gazan cease-fire is so that the participants in the Israeli conflict can be sent to address the growing threat of ISIS."
The June document explicitly declares that the new caliphate is established "for the purpose of compelling the people to do what the Sharia (Allah's law) requires of them." In ISIS' view, that means anyone who doesn't believe in its severe interpretation of Islam must convert or die.
The simplicity and specificity of ISIS' message have helped it attract fighters from all over the world, including several dozen Americans, U.S. officials have told NBC News. That has given it a legitimate shot at displacing al-Qaeda itself as the world's foremost terrorist "brand," the officials said.
Scholars and U.S. intelligence officials told NBC News that ISIS is the wealthiest terrorist group in the world, having raked in hundreds of millions of dollars in the past two years.
"It's like the Mafia. When it sees an opportunity to make money; it jumps in with both feet," Austin Long, an assistant professor specializing in security policy at Columbia University, told NBC News last month.
"Historically, they've made money on everything from protection rackets to carjacking to people's donations," Long said. "Now, they're selling resources they've taken from oil fields and oil refineries ... [and collecting] ransom" for kidnap victims.
ISIS vacuums up money at such an alarming rate because it's spending it just as quickly — "running a caliphate is not cheap," a U.S. official told NBC News, ticking off "the cost of governance [and] paying administrators in the towns and cities they have captured and incorporated."
Revenge — especially against the U.S.
ISIS sprang up in the aftermath of the U.S. occupation of Iraq, and al-Baghdadi himself was imprisoned by U.S. forces in Iraq from 2005 to 2009.
In an email it sent to the parents of James Foley, the American journalist whom it executed last month, ISIS said it was acting "as a DIRECT result of your transgressions towards us!"
The message cited recent U.S. airbombings of suspected ISIS positions and Washington's refusal to negotiate the release of Muslims detained by the U.S., vowing: "WE WILL NOT STOP UNTILL WE QUENCH OUR THIRST FOR YOUR BLOOD."
It's a bloodthirsty message that ISIS spreads in a very sophisticated manner, said Hudson, the Middle East scholar at the University of Arizona, who said it would be a grave mistake to presume that because ISIS' message is primitive, the group itself is primitive.
The group's "horrific utilization of social media and these barbaric videos that they have put out" have been "quite successful in creating situations that the world needs to react to immediately," she told NBC News.
"You can respond one by one in a reactive manner, but that's sort of what they want," she said. For the U.S. to "take a very low-level reactive and tactical response is not a solution."
Editor's note: A previous version of this story incorrectly reported that Leila Hudson of the University of Arizona described ISIS fighters as Shiite Muslims. They are not Shiite, and Hudson did not describe them that way.