A soldier from the Iraqi Security Forces ran out of ammunition in the midst of a firefight with Islamic State in Iraq and the Levant (ISIL) forces in Fallujah, Iraq in May of last year. After being wounded the soldier was captured by ISIL, paraded around as a prize, and—in a scene reminiscent of the four U.S. contractors killed in 2004—was hung from Employees’ Bridge in Fallujah.

On November 13, 2014, 16 members of the Sunni Arab Albu Nimr tribe were abducted from their homes by ISIL near Tharthar Lake in Anbar province. With one woman and two children among them, the tribal members were driven to Shtyah area and all were summarily executed by ISIL fighters. Their crime: being related to Sahwa militia fighting ISIL near Hit.

The level of brutality exhibited by these executions is unlikely to shock many. Similar stories of ISIL’s atrocities have been widely reported for over two years now. However, there is a surprising difference between the two events described above. While the execution of the Iraqi soldier was proudly posted to social media by ISIL, the executions of the family members of Sahwa militia fighters was hidden. The only reason I can report the atrocity is because of a United Nations mission to investigate human rights violations in Iraq. What also may come as a surprise is that this pattern of disclosure and non-disclosure of executions follows a distinct pattern by ISIL in Iraq. The reasons for the pattern may point to an effective way to dissuade people from joining ISIL.

State Department officials remain quite vague on how they are currently countering the Islamic State of Iraq and the Levant’s (ISIL) recruitment efforts. However, the State Department’s website does make it clear that highlighting the contradictions between ISIL’s recruitment messaging and its acts of brutality represents a large part of the counter-recruitment strategy. But are there further acts of brutality committed by ISIL that, if made public, could possibly dissuade recruits? A quantitative dataset I constructed from five recent U.N. Assistance Mission for Iraq (UNAMI) reports covering ISIL’s executions between June 2014 and October 2015 in Iraq helps to answer this question.

The data shows that ISIL is selective about which executions are publicized on social media and which are kept private. The group publicizes the executions of captured enemy fighters and collaborators on social media, but not those of innocent civilians. This dissonance between the overall nature of the group’s execution campaign and how it is represented in public could represent an opportunity for the State Department and other organizations seeking to dissuade people from joining ISIL. Highlighting the executions that are kept private will be more effective in dissuading potential recruits than broadly pointing to all the executions of Muslims as contradictory to ISIL’s branding as defenders of Islam.

Of the 1,754 people executed by ISIL on social media in Iraq between June 2014 and October 2015, 98 percent were captured combatants or suspected of collaboration with the enemies of ISIL. It should not be surprising to the general public that ISIL believes potential recruits — especially those already sympathetic to the group’s ideology — might be motivated by the executions of those actively seeking the destruction of “the caliphate.” Social scientists have demonstrated that individuals and even entire societies can be turned homicidal toward other groups seen as threats.

These numbers help explain why the State Department’s video, “Welcome to ISIS Land,” was such a failure — as State Department officials now admit. By using videos of ISIL’s executions, the State Department intended to show potential recruits that the extremist group is not the defender of Islam, but instead the murderer of innocent Muslims. Critics argued that the video helped ISIL by bringing more attention to executions the group obviously wanted to be seen in the first place. My findings back up the critics.

Interestingly, however, the number of people executed on social media makes up only 29 percent of the 6,019 people executed by ISIL in my dataset.

So which executions didn’t make it to social media?

Yazidi civilians make up the largest excluded group at 1,218 executions. Family members of (mainly Sunni Arab) Muslim tribes fighting ISIL come in second at 274. The final two groups are women and children at 135 and 14, respectively. It is tempting to simply conclude that the State Department efforts to counter ISIL’s narrative should focus on highlighting these executions. However, looking deeper into the characteristics of each group reveals some important nuances.

For instance, pointing to the overall genocide of Yazidis will not be very effective. A recent U.N. report on the genocide shows that while ISIL may have not shown these executions on social media, the group has made public statements explicitly justifying these mass killings. The justification boils down to the fact that — unlike Christians and Jews — Yazidis do not worship the same God as Muslims. Thus, if Yazidis do not convert, they are deemed a threat to the caliphate and must be killed. Similarly, ISIL has provided justification for killing Shiite civilians by arguing that the sect’s religious practices violate basic tenants of the Quran. Noticeably, however, ISIL does not discuss the killing of Yazidi children. My dataset features four Yazidi children executed by ISIL, though the U.N. genocide report indicates there are many more.

Unlike Yazidis, it is possible that highlighting the executions of families of Sunni Arab tribal fighters could damage ISIL’s brand. ISIL has publicly condemned the killing of Sunni Arabs. In fact, while praising the barbarity of the now deceased Al-Qaeda leader Abu Musab al-Zarqawi in the first issue of its English-language Dabiq magazine, ISIL assures its readers that “Obviously, [Zarqawi’s] operations never targeted Sunni public places and gatherings – contrary to the claims of the crusader and apostate media.” However, the majority of family members of fighters executed by ISIL come from the Sunni Arab Albu Nimr and Jabouri tribes. Admittedly, it is very likely that an ISIL spokesman would characterize family members of Sunni tribal fighters as collaborators. Still, ISIL’s silence on these killings speaks volumes, especially when it comes to the two children of tribal fighters killed alongside their parents.

Clearly, counter-recruitment efforts should focus on highlighting ISIL’s brutality toward Sunni Arabs, and children of all faiths and ethnicities. But what about women?

ISIL provides a justification for killing both Yazidi and Shiite women. However, of the 135 women executed, the overwhelming majority appear to be Sunni Arab, based on the fact that almost all of these killings took place in Mosul. Among the women killed, most (77) were Iraqi government officials or other professionals. Although women in ISIL territory do help the group recruit on social media and even serve in their police force, it is clear that the idea of women in government or other elite positions is antithetical to ISIL’s ideal caliphate. Still, the group has provided no justification for these killings and tries to keep these scenes of brutality from the public eye.

The second largest group of women executed by ISIL are those that refuse marriage and sex to ISIL fighters. It is difficult to ascertain the ethnicity or the religion of these women from the data. However, as more research on the identities of these women comes to light, it is important for future counter-recruitment efforts to keep in mind that ISIL does provide justification for killing Yazidi women for refusing sex and marriage, but not Sunni Arab women.

The data shows that there are indeed acts of brutality that ISIL would rather stay hidden. But as any honest social scientist will admit, there is no guarantee that highlighting the killing of children and Sunnis would turn away recruits. Nor is there any reliable way to measure the effectiveness of such messaging. For instance, it is not plausible for researchers to poll a representative sample of potential recruits that seriously contemplated joining ISIL, but decided not to. The State Department has surveyed defectors, but analysis of this population alone does not sufficiently allow for an understanding of the effectiveness of specific messaging. Second, the recent finding that ISIL’s foreign recruitment is down 90 percent is clearly tied to financial and battlefield losses, making it impossible to study messaging in isolation.

These two factors may lead policymakers to wonder whether the resources allocated to the State Department’s counter-recruitment effort should be reallocated toward defeating ISIL on the battlefield. The answer to this query requires further research or at least some frank discussions with non-partisan research methodologists. However, my findings show that—contrary to popular belief—there are in fact acts of brutality that even ISIL doesn’t want made public, and that highlighting these atrocities is the best way to chip away at the facade that brings in so many recruits.

Patrick Burke is a researcher at the Chicago Project on Security and Terrorism (CPOST), and recently graduated from the University of Chicago with an M.A. in International Relations. Prior to his current career Patrick spent three years in the Air Force as an air traffic controller, and five years in the Illinois Air National Guard as a member of the Tactical Air Control Party. If you are interested in receiving the dataset from this article please email Patrick at patrick.j.burke6112@gmail.com.