On Saturday, a theory began circulating about why the Islamic State, also known as ISIS and ISIL, attacked Paris: Since the Islamic State's drive to gain and hold territory in Syria has suffered setbacks lately, perhaps the group was lashing out to kill people far beyond its borders to compensate.

“This switch toward killing people, toward terrorism is, I think, a sign of their weakness,” Audrey Kurth Cronin, director of George Mason University's international security program, said on National Public Radio. "They've lost Sinjar. There was also the killing of Jihadi John. And I think that ISIS is feeling that they need to regain the momentum, that they need to capture people's attention, and they see themselves as using terrorism in order to do that."

Cronin was referring to Kurdish forces retaking a region in northern Iraq, and a U.S. drone strike on the Islamic State's headquarters in the Syrian city of Raqqa that killed a Kuwaiti-born British militant who had appeared in several videos of hostages being beheaded.

But the story is a bit more complicated, experts say. First, they point out, the planning for attacks like those one in Paris would need to have started long before those recent reversals.

"I think this level of operation is far too sophisticated for this to be a response to Sinjar or Jihadi John,” said Mila Johns, a researcher at the National Consortium for the Study of Terrorism and Responses to Terrorism.

The scene in France after bloody rampage stuns Paris

U.S. President Barack Obama, right, and French President Francois Hollande pay their respect at the Bataclan concert hall, one of the recent deadly Paris attack sites, after Obama arrived in the French capital to attend the World Climate Change Conference 2015 (COP21), Monday, Nov. 30, 2015. (Philippe Wojazer, Pool via AP)

And second, even though the Islamic State had focused mostly within its own region until the past few months, it has long been the group’s intention to strike far beyond its borders.

Warnings of attacks on a Western nation started last year, with messages from ISIS leaders exhorting adherents to kill enemies of Islam wherever they find them — which in recent months had turned to France specifically.

"Those Western government officials and academic ‘experts' who were claiming that the IS was focused entirely on carrying out operations in territories in Iraq, Syria, or other Muslim countries, thereby suggesting that the group did not represent a serious threat to the West, have been wrong all along,” says Jeffrey Bale, a professor at the Middlebury Institute of International Studies at Monterey who has long studied terrorist behavior. "All one has to do to understand the motives and goals of Islamist groups is to pay attention to what they themselves are openly and, indeed, proudly saying.”

All the same, there is reason to believe that the Islamic State's defensive posture in its homeland might be related to the group’s growing aggression abroad.

According to Gina Ligon, an associate professor of management at the University of Nebraska at Omaha who has extensively studied the group’s organizational structure, violence against civilians can be a fundraising tool. The group is “fastidious” about documenting return on investment for its funders, creating promotional videos and collecting news articles about their handiwork to demonstrate impact.

“One of the unfortunate consequences [of the Paris attacks] is that they are getting a lot of bang for their buck, so we imagine they will use the fallout to find more donors so they can finance future attacks,” Ligon says.

But the Islamic State doesn’t need just capital to survive and spread — it also needs labor, in the form of new recruits. Such attacks are a propaganda tool, Ligon says, making the group look stronger in relation to other terrorist groups. “When [the Islamic State] feels like their land is at risk, this is their go-to strategy,” Ligon says.

Finally, there’s also research to suggest a pattern behind the group’s behavior. Victor Asal, co-director of the Project on Violent Conflict at the State University of New York-Albany, has analyzed the comparative behavior of hundreds of extremist groups, including how they respond to “carrots” (such as negotiation and dealmaking) and “sticks” (such as airstrikes). Those being pounded with “sticks” tend to respond in kind, while those being tempted with "carrots” are less likely to launch attacks.

Now, the latter approach might not work with a group such as the Islamic State. Asal figures that the only option that France, the United States and their allies have is to try to wipe out the Islamic State militarily. But that will almost certainly engender more attacks, until the group has been subdued to the point where it lacks the capacity to mount them.

"The question is, 'Does the U.S. have the wherewithal to do this until it's done?’” Asal says. “If they don’t, what you do is you tick people but you don’t finish the job. And that's really bad."

Asal, Johns and Ligon say the Europeans would make things worse by becoming more hostile to the millions of refugees who have been flowing in from Syria, fleeing the very same force that visited so much terror upon Paris. Most of the Islamic State's recruits — and the most valuable — are people who have been radicalized in their own countries. Cracking down on migrants would only exacerbate the problem, the experts say.

“I would be very hesitant to say that the increase in refugee flows is going to be an increase in risk,” Johns says.