According to the Pentagon, less than 100 military personnel are believed to have been involved with substantiated extremist activities in the last year. They warn, however, that this number could rise due to recent spikes in violent extremism within the domestic population, especially among veterans.

Officials stated that the new policy does not significantly change what is allowed, but it is more an attempt to ensure troops know what they can and cannot do while protecting their First Amendment right of free speech. It is also more specific about social media for the first time.

The policy details the prohibited activities. They include advocating terrorism and supporting the overthrow or government, fundraising for extremist groups or sharing extremist views via social media. To hold someone accountable, commanders must establish that the action was extremist as per the rules and that the service member "actively took part" in it.

Although previous policies prohibited extremist activities, they didn't provide sufficient detail and did not outline the two-step process for determining who was responsible.

One senior defense official said that what was wrong yesterday is still wrong today. However, several officials stated that they spoke to service members in this year's study group and found that many wanted more clear definitions of what was allowed. Officials provided further details on the rules under condition of anonymity, as they weren't made public.

Since the beginning, the military was aware that there were small numbers of white supremacists within its ranks. After it became apparent that some military veterans and current service members were present during the Jan. 6 rebellion, Defense Secretary Lloyd Austin and others launched a larger campaign to eradicate extremism within the force.

Austin sent a message Monday to the force, stating that the department believes only a handful of service members are guilty of violating their oaths and participating in extremist activities. Austin said that even the actions of a few could have a significant impact on unit cohesion and morale, and that the physical harm these activities can cause can threaten the safety of our citizens.

Extremism can be even more dangerous in the military because service personnel have access to classified information on sensitive military operations and other national security information that could aid adversaries. Extremist groups regularly recruit ex-servicemen and current military personnel because they are familiar with combat tactics and weapons.

Although the number of cases that have been substantiated may seem small, it is still significant in comparison to the military's 2 million reserve and active troops. The number of substantiated cases appears to have increased over previous years, when they were only in the mid-two-digits. Officials also pointed out that the data is not consistent and it is hard to spot trends.

The new rules don't provide a list of terrorist organizations. Officials said that commanders will determine whether a service member is engaged in extremist activities on the basis of the definitions and not on a constantly changing list.

Officials said that troops cannot be simply members of extremist organizations. They also denied that dues payments or any other actions could be considered "active participation."

John Kirby, a Pentagon spokesperson, told reporters that there is not much about membership in a group you can get away with. He also said that it was likely that you will be caught violating one of these criteria to prove your membership.

Kirby stated that commanders will assess each case individually. So, simply liking one post on social media might not be grounds for punishment, depending on the circumstances.

He also pointed out that the Pentagon doesn't have the capability or desire to monitor individual social media accounts of troops. These issues could be reported to commanders, or discovered by other means.

These regulations define six main types of extremist activities, and 14 definitions of active participation.

Austin, shortly after his election, ordered military leaders to set aside a "stand down" day to talk to their troops about extremism.

All military services are affected by the new rules, except the Coast Guard which is, in peacetime, part of the Department of Homeland Security. These rules were developed from recommendations by the Countering Extremist Activities Working Group. They make distinctions, such as that troops can possess extremist material, but they cannot attempt to distribute it, and they can only observe extremist rallies, but not fund, finance, or support them.

Officials stated that the rules are based on behavior and not ideology. Service members can have any political, religious, or other belief they wish, but their actions, and behavior, are controlled.

The Pentagon has expanded its screening process for potential recruits to take a closer look at extremist activities in addition to the new rules. While some activities might not completely prevent someone from joining, others may require that the Pentagon take a closer look at the applicant.

The department is also expanding education and training for military personnel, but more specifically for service members leaving who might be subject to extremist recruitment.

Insurrection at Capitol Jan. 6, 2017, saw more than 650 people charged, including about half a dozen veterans and a few active-duty service personnel.