clip_35In 2015, at a global conference on sexual violence during war, many speakers agreed that the best way to deter such crimes was prosecution, and they called for more of it. But prosecutions are not enough. We must work to reduce sexual violence by armed groupsduring wars — not just act afterward.

First, we have to better understand it. Although rape during war is an ancient crime, it’s only in the last decade that social scientists have begun to study the patterns in which soldiers and rebels rape. The findings may be surprising: It’s not more likely to occur in particular regions, countries with greater gender inequality or during ethnic conflict; men may be victims, and women can be perpetrators.

But while rape is tragically common in war zones, it’s not an inevitable part of war. In fact, we have found that a significant percentage of both armies and rebel groups in recent civil wars were, surprisingly, not reported to have raped civilians. That’s because commanders have options: They can choose to order, tolerate or prohibit rape. A deeper understanding of their behavior offers the hope of mitigating the problem.

Some commanders order rape as a military or political strategy, and specify the target. As the Soviet Army marched toward Germany in 1945, generals ordered soldiers to take revenge on all Germans, not just soldiers. Guatemalan soldiers systematically raped indigenous Mayans during the civil war from 1960 to 1996. Today, the Islamic State forces Yazidi women and girls into marriages and sexual slavery, which they wrongly believe is legitimate under Islamic law.

Other commanders, even when they don’t order rape, implicitly or explicitly tolerate it. And rape can become extremely widespread, although it’s not ordered. In these cases, we have found that the motivation to rape often comes from soldiers’ interactions with one another.

It may reflect soldiers’ frustration in fighting an enemy that is difficult to engage, as it was for those units of American troops who raped Vietnamese civilians in the 1960s. It can also be a form of self-pay, as it is for Congolese soldiers who say that they rape out of anger that their meager salary prevents them from achieving masculine ideals, like providing for a family. Gang rape, in particular, may allow soldiers who were conscripted by force to create bonds of friendship and loyalty, as male and female members of the Revolutionary United Front in Sierra Leone reported.

Finally, some commanders prohibit rape by their soldiers. In Sri Lanka the Tamil Tigers, while otherwise very violent during their insurgency in the 1980s and ’90s, closely monitored their troops and brutally punished the few soldiers who raped. In El Salvador in the 1980s, commanders of the Farabundo Martí National Liberation Front required their fighters to attend classes that emphasized that the group’s Marxist ideology prohibited the abuse of civilians. Rape was already infrequent, but after classes started, it virtually ended. Although both the Israel Defense Forces and Palestinian militant groups commit other acts of violence, rape has been extremely rare in recent years.

Unlike a stray bullet, rape is always intentional — whether it’s ordered from above or emerges from below. That simple fact means there is a lot that military officers and leaders of insurgent groups, NGOs and government agencies can do to mitigate it.

To counter rape during war, the international community has focused heavily on increasing prosecutions. Prosecutions are important because they confirm to survivors that rape is a crime and an injustice. But prosecutors often seek evidence of an explicit policy. This leaves out commanders who tolerate rape, even if they don’t order it. They, too, should be held responsible.

Moreover, prosecutions are insufficient. Trials are too costly, slow and small in scope. And there is little evidence to suggest they have a deterrent effect.

Instead, we should work to prevent rape during conflicts. To do so, we must understand specific traits of armed groups — their ideology, morals and laws, as well as how commanders recruit, discipline and pay soldiers — which can help predict whether a group might rape, and how.

Scholars have found that organizations that recruit by kidnapping are significantly more likely to perpetrate widespread gang rape than those that don’t. Groups that torture detainees are more likely to engage in sexual violence as well. These characteristics, if better understood, could serve as early warning signs for those who want to prevent rape from happening or worsening once it starts.

For instance, armies that rape should be publicly named and shamed, a tactic that research shows significantly ameliorated the severity of genocides and state-sponsored killing in the last several decades. If a soldier is widely identified as a rapist, or a commander is known around the world to tolerate rape, the shame and threat to their reputation may dissuade their peers — particularly those who seek international legitimacy — from raping.

Countries should make aid and weapon transfers to armed groups conditional on their human rights record and swiftly withdraw both if soldiers are reported to rape civilians. And they must punish leaders of armed groups who order or tolerate rape by imposing targeted sanctions, like travel bans and asset freezes. These options may convince leaders of armed groups that the cost of rape is too high.

Such tactics won’t work with groups like the Islamic State that reject international law and do not rely on external funding. Instead, the testimonies of recruits who have defected could become powerful deterrents if they are widely publicized.

Moreover, many Muslim scholars around the world have rejected the Islamic State’s interpretation of their faith. Some prominent jihadists have even called it “deviant.” These figures have the credibility that Western policy makers lack to critique the Islamic State’s ideology.

Thanks to the courageous work of lawyers and activists, rape is no longer “the greatest silence.” Many survivors around the world report it, despite the significant risks. The challenge today is not to make an invisible crime more visible. It is to apply what has been learned over the past decades to prevent it.

Elisabeth Jean Wood, a professor of political science at Yale, is the author of the forthcoming book “Sexual Violence During War.” Dara Kay Cohen, an assistant professor of public policy at Harvard, is the author of the forthcoming book “Rape During Civil War.”