Daryl Johnson, former senior domestic terrorism analyst at the Department of Homeland Security, noted the important relationship between the military and violent right-wing extremism in his book Right Wing Resurgence. He writes that right-wing extremists "target law enforcement and military personnel for their training experience (particularly weapons and explosives training), their disciplined way of life, leadership skills, and access to weapons, equipment, and sensitive information." Johnson further notes that a government survey of 17,080 soldiers found that 3.5 percent of them had been contacted in order to recruit them into an extremist organization and that 7.1 percent said they knew another soldier who they believed to be part of an extremist organization.

The New America Foundation's dataset on homegrown extremists offers a platform to quantitatively compare the threat from military-trained right-wing and jihadist extremists, and to evaluate the significance of the threat from each form of extremism. The dataset includes those extremists indicted or involved in violent activities since 2001. According to the dataset, 13 jihadist and Al Qaeda-linked homegrown extremists served in the US military, and they account for about six percent of jihadist extremists listed in the database. These jihadists do appear to be more dangerous than jihadists who have not served in the military. They are more likely to acquire arms on their own, for example. Furthermore, about twenty-five percent of those who served in the military were involved in violent incidents compared to six percent of all jihadist extremists in the dataset. In terms of raw numbers, the threat of jihadist extremists with experience serving in the US military appears to have held steady or possibly to have declined since 9/11. Slightly over half of the cases involved indictments or incidents prior to 2005, though five cases since 2008 suggest a continued risk.

So the dataset does provide support for those worrying about the increased security risk of military-trained jihadists. Yet the threat pales in comparison with the threat from right-wing extremists with US military training. While only 13 jihadists had served in the US military, 21 right-wing extremists served in the US military. It's a particularly striking number because there are nearly 100 fewer right-wing extremists listed in the dataset. Moreover, in contrast to the military-trained jihadist threat, the threat from right wing extremists with military training appears to be growing. About 70 percent of the right-wing extremists who have served in the military were indicted or were involved in an incident since the beginning of 2008.

Another sign of the risk from military-trained right wing extremists: They've committed more attacks -- more than twice as many as their jihadist counterparts. Just under half of military-trained right-wing extremists were involved in incidents compared to under one-fourth of military-trained jihadist extremists. As with the jihadists, military service among right-wing extremists is correlated with an increase in rates of violent incidents compared to those without military service, though the effect appears to be smaller than among jihadists: About 48 percent of those who served in the military were involved in incidents compared to about 44 percent of all right-wing homegrown extremists.