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The Proud Boys and Oath Keepers allegedly teamed up for the Capitol invasion. Should we worry?

Here’s what we know about what happens when armed militant groups collaborate

Prosecutors have accused far-right groups of organizing in advance of the Capitol attack on Jan. 6. (Jim Bourg/Reuters)
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Two of the far-right groups accused of involvement in the Jan. 6 Capitol violence apparently “organized an alliance” in the days before the insurrection.

How often and why do militant groups coordinate their violence — and what are the possible effects? Here’s what researchers know about collaboration among militant groups.

How often do armed groups cooperate?

It’s difficult to know exactly how common this behavior is, because militant groups often operate under the radar, trying to avoid government scrutiny. But scholars have analyzed many cases in which armed groups team up for everything from sharing knowledge to joint training and attacks.

For example, members of the Irish Republican Army apparently helped train the Revolutionary Armed Forces of Colombia in making bombs. Palestinian groups sometimes train and attack together. During civil conflict, rebel groups often join alliances, if they are fleeting.

In my own research, I examined the activity of hundreds of militant groups around the world between 1987 and 2005. About half had cooperated with another militant group on logistics, training or attacks.

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Why do armed groups cooperate with each other?

Teamwork can pay off in several ways. A few studies have found that, when allied, militant groups tend to kill more people than those operating independently.

Militant groups can learn new tactics from their partners. Some argue that the global diffusion of suicide bombing is one such case.

As militant groups learn from each other and share resources, those in alliances tend to survive longer than groups that go it alone, some of my research shows. Furthermore, the survival-enhancing benefits of alliances seem to be strongest in environments where militant groups would otherwise have a harder time operating — in countries with more capable governments.

And during civil wars, rebel groups with strong alliances are more likely to defeat the government.

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Which types of groups tend to link up?

Not surprisingly, militant groups sharing the same ideology are the most likely to work together. Collaboration between the Proud Boys and the Oath Keepers would fit this pattern.

Some research has found that pairs of groups that are ethnically or religiously motivated are especially likely to work together, too.

Groups are also more likely to work together if they share a foreign state sponsor. It can also be helpful if one especially powerful group, a “hub,” such as al-Qaeda, can coordinate relationships.

Some observers believe that militants cooperate only when they’re weak and unable to operate on their own. But research hasn’t consistently found a link between group strength or weakness and propensity to form alliances. In fact, some analysts find that group resources don’t seem to matter, or matter only in certain conditions, for explaining militant group alliances.

A few studies find that medium-size groups are the most likely to team up with others. That’s what political scientist Kanisha D. Bond finds in her analysis of such groups in Latin America, arguing that it’s because small groups are unable to find partners, while the largest groups don’t have incentives to join with others. My research on a global sample of militant groups confirmed her findings.

Why is cooperation somewhat risky — and not more common?

Many militant groups do not collaborate with their peers. As political scientist and terrorism expert Tricia Bacon notes, such cooperation can be dangerous. It can invite government attention. Clandestine groups are often suspicious of one another and concerned about sharing secrets with a group that could be infiltrated by government agents or that might eventually cooperate with authorities.

Beyond this, groups cooperating with one another are vulnerable in other ways. International relations scholar Yasutaka Tominaga shows that when a government arrests the leader of one militant group, this seems to deter other groups from using violence. But the deterrent effect is even stronger among the targeted group’s allies.

Somewhat related to this, new research shows that capturing or killing a militant group’s leader breaks down alliances in which the group had been involved.

What should we watch for?

In sum, cooperation among militant groups can make them stronger and more lethal. But group interdependence can sometimes mean vulnerability. If governments can identify and exploit such vulnerabilities, this helps counterterrorism or counterinsurgency efforts.

What does this all mean for the Proud Boys and the Oath Keepers? The key question is whether their alleged alliance made the violence they are accused of committing more potent — or helped the government arrest their members. We’ll see as the investigation continues.

Will these two groups remain allied? If so, how will it affect their future activities?

The answer to the first question depends on to what extent law enforcement disrupted their operations after the Capitol violence. If the groups remain viable, it is likely that they will continue to cooperate on their shared interests. The potential benefits of this cooperation for the groups should concern investigators — but the alliance would also provide potential vulnerabilities that could be exploited.

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Brian J. Phillips (@brian_jphillips) is a reader at the University of Essex and an affiliated professor at Centro de Investigación y Docencia Económicas (CIDE).