Despite the existence of a good deal of research about terrorism, there’s a gap between the common understanding of what leads terrorists to kill and what many experts believe to be true.

Terrorist groups like ISIS and Al Qaeda are widely seen as being motivated by their radical theology. But according to Robert Pape, a political scientist at the University of Chicago and founder of the Chicago Project on Security and Terrorism, this view is too simplistic. Pape knows his subject; he and his colleagues have studied every suicide attack in the world since 1980, evaluating over 4,600 in all.

He says that religious fervor is not a motive unto itself. Rather, it serves as a tool for recruitment and a potent means of getting people to overcome their fear of death and natural aversion to killing innocents. “Very often, suicide attackers realize they have instincts for self-preservation that they have to overcome,” and religious beliefs are often part of that process, said Pape in an appearance on my radio show, Politics and Reality Radio, last week. But, Pape adds, there have been “many hundreds of secular suicide attackers,” which suggests that radical theology alone doesn’t explain terrorist attacks. From 1980 until about 2003, the “world leader” in suicide attacks was the Tamil Tigers, a secular Marxist nationalist group in Sri Lanka.

According to Pape’s research, underlying the outward expressions of religious fervor, ISIS’s goals, like those of most terrorist groups, are distinctly earthly:

What 95 percent of all suicide attacks have in common, since 1980, is not religion, but a specific strategic motivation to respond to a military intervention, often specifically a military occupation, of territory that the terrorists view as their homeland or prize greatly. From Lebanon and the West Bank in the 80s and 90s, to Iraq and Afghanistan, and up through the Paris suicide attacks we’ve just experienced in the last days, military intervention—and specifically when the military intervention is occupying territory—that’s what prompts suicide terrorism more than anything else.

ISIS emerged from the insurgency against the US occupation of Iraq just as the Al Qaeda network traces its origins to the Afghan resistance to the Soviet occupation in the 1980s.

This view differs from that of Hillary Clinton and others who believe that ISIS “has nothing whatsoever to do” with Islam, as well as the more common belief, articulated by Graeme Wood in The Atlantic, that ISIS can be reduced to “a religious group with carefully considered beliefs.” It’s a group whose outward expressions of religious fervor serve its secular objectives of controlling resources and territory. Virtually all of the group’s leaders were once high-ranking officers in Iraq’s secular military.

Pape’s analysis is consistent with what Lydia Wilson found when she interviewed captured ISIS fighters in Iraq. “They are woefully ignorant about Islam and have difficulty answering questions about Sharia law, militant jihad, and the caliphate,” she recently wrote in The Nation. “But a detailed, or even superficial, knowledge of Islam isn’t necessarily relevant to the ideal of fighting for an Islamic State, as we have seen from the Amazon order of Islam for Dummies by one British fighter bound for ISIS.”

But how does the notion that terrorists are intent on getting powers to withdraw from their territory square with the view that the group’s shift to terrorist attacks in the West is designed to draw France and its allies into a ground war in Syria? Writing at the Harvard Business Review, Northeastern University political scientist Max Abrahms argues that these analyses are contradictory. But Pape says that it’s important to distinguish between ISIS’s long-term goals and its shorter-term strategies to achieve them:

It’s about the timing. How are you going to get the United States, France and other major powers to truly abandon and withdraw from the Persian Gulf when they have such a large interest in oil? A single attack isn’t going to do it. Bin Laden did 9/11 hoping that it would suck a large American ground army into Afghanistan, which would help recruit a large number of suicide attackers to punish America for intervening. We didn’t do that – we used very limited military force in Afghanistan. But what Bin Laden didn’t count on was that we would send a large ground army into Iraq to knock Saddam out. And that turned out to be the most potent recruiting ground for anti-American terrorists that ever was, more so than Bin Laden had ever hoped for in his wildest dreams.

So if your goal is to create military costs on these states and get them to withdraw, you’ve got to figure out a way to really up the ante. And the way that you really up the ante is to get them to overreact. You try to get them to send a large ground army in so that you can truly drive up the costs. That’s what ISIS is trying to sucker us into doing.

Another theory holds that ISIS—and Al Qaeda—set their sights on France in order to polarize mainstream French society against its Muslim community. As University of Michigan historian Juan Cole put it after the Charlie Hebdo attacks, “The problem for a terrorist group like Al Qaeda is that its recruitment pool is Muslims, but most Muslims are not interested in terrorism. Most Muslims are not even interested in politics, much less political Islam.” In Cole’s formulation, if violent Islamic fundamentalists “can get non-Muslim French to be beastly to ethnic Muslims on the grounds that they are Muslims, it can start creating a common political identity around grievance against discrimination.”

Pape says this analysis is also consistent with his research:

If ISIS is going to end the military intervention by France, one attack is not likely to do it. In the statement that ISIS released, they say that they want a storm of similar attacks against Paris and other French targets because their goal is to knock France out of the military coalition. To do that, to achieve that goal, they’re going to need to recruit many more attackers to do suicide attacks like the ones that occurred in Paris. In the short-term it makes perfect sense to want an environment that stirs up hostility towards Muslims in France, because that will make them much easier to recruit for their longer-term object of kicking France of the coalition.

Pape also argues that ISIS’ shift in strategy to attacks overseas is a sign not of its strength, but of its weakness on the ground in Syria and Iraq. He points out that over the past year, the amount of territory ISIS controls has shrunk by 10 percent:

The U.S. strategy against ISIS is working and it’s putting enormous pressure on ISIS. It’s a strategy of air and ground power, with the ground power coming from local allies—the Kurds and the Shia in the region, and even some Sunnis who are opposed to ISIS. They’re increasingly working with us on the ground while we’re fighting from the air. The problem here is not that we don’t have enough ground forces.

It’s because the strategy is working that ISIS is now desperate, and is shifting its pattern of behavior. In October, ISIS launched only eight suicide attacks in Iraq and Syria, when they normally do 30 to 35 per month, and that’s the same month that they shifted to suicide attacks in Ankara, Turkey, on October 10. Then they downed the Russian plane on October 31st, and now the Paris attacks on November 13th. As ISIS’ territory has shrunk in Iraq and Syria, it is now clearly shifting its suicide attack resources out of Iraq and Syria, and into Turkey, into killing Russian civilians, and now also into Paris.

In Pape’s view, most of the conventional wisdom about what terrorists want to achieve is wrong, and that disconnect has limited the effectiveness of the West’s response to terrorism.

Robert Pape’s responses have been condensed and edited for clarity. You can listen to the entire 18-minute interview below.

You can also download the whole show at iTunes. It also featured Rebecca Hamlin, an assistant professor of legal studies at the University of Massachusetts Amherst and the author of Let Me Be a Refugee: Administrative Justice and the Politics of Asylum in the United States, Canada and Australia, discussing Syrian refugees, and Salon columnist Heather “Digby” Parton talking about the ugly politics of terrorism.

Editor’s Note: An earlier version of this piece described the Tamil Tigers as “a secular Marxist group of Hindu nationalists in Sri Lanka.” Though the majority of Tamil Tigers are Hindu, the conflict is not religious and not all group members are Hindu, so that part of the descriptor has been removed.