What to Know About the Virginia Gun Rally

What is the Base?

The authorities on Thursday announced the arrests of three men linked to the Base, an extremist group being tracked by the F.B.I. The three men had obtained weapons and discussed participating in the Richmond rally and were charged with various federal crimes in Maryland, the authorities said.

On Friday, law enforcement announced the arrest of at least four other men also tied to the Base, in separate plots. In Georgia, three men, who are members of the group, were arrested and charged for a conspiracy to murder a married couple in Bartow County, the authorities said.

In Wisconsin, another member of the Base was arrested on charges of vandalizing a synagogue in Racine, Wis., according to court documents.

The Base is a white extremist, antigovernment group that aims to establish a white “ethno-state.”

The F.B.I. has grown increasingly concerned about the Base as it has worked to recruit more people. The group encourages the onset of anarchy, according to the Counter Extremism Project, an organization that tracks far-right extremists. Experts say that its founder, an American, appears to be living in Russia.

Former law enforcement officials say the Base and a similar group known as Atomwaffen have become priorities for the F.B.I.

In November, the F.B.I. arrested Richard Tobin, a young man in New Jersey, who was accused of recruiting on behalf of the Base and of supporting violence, including the killing of black people with a machete.

How long will the state of emergency last?

Mr. Northam declared a state of emergency ahead of Monday’s rally, temporarily banning weapons, including firearms, from the grounds of the State Capitol in a move that the Virginia Citizens Defense League tried to fight in court.