A movement, driven underground and shorn of its more moderate elements, may seek methods of amplifying its message and heightening conflict. And at its most basic, terrorism is violent communication and an economical form of violence. It requires only a modest deployment of effort and resources to achieve a large psychological shock effect. The act itself communicates a message.
Terrorism can also provoke retaliation — which might involve government repression or even exactly the sort of race war or apocalyptic conflict some far-right militants seek. The political scientist Ian Lustick once described one form of terrorism as “solipsistic” violence intended to excite the faithful, not terrify the enemy. The question is how to prevent an endless spiral of violence generated by radicalization and countermobilization.
The substrate from which terrorism blossoms, though, is verbal and visual communication. Technology enables the far-right and conspiracist world to communicate remotely, binding together the movement, but also increasing distrust and fear of infiltration. The result is that democracies must search for ways to combat propaganda and disinformation and to make it harder to recruit and raise funds.
As a result, governments and private enterprises such as Facebook and Twitter have responded to online appeals for violence by restricting extremists’ ability to communicate. There are precedents for suppression; the British government, for example, at one point tried to keep the I.R.A. off radio and television.
But in democracies such restrictions come up against rules and norms protecting freedom of speech, association and assembly, so countermeasures that restrict access to communication or outlaw particular groups are predictably contentious, adding to distrust of government. This paradox is faced by all democracies.
As such, this is not just a question for the Biden administration. Spectacular terrorist attacks attract imitators elsewhere. This trend is related to “lone wolf” terrorism — when individuals act without the logistical support of a group. But these “lone” terrorists often consider themselves as members of a group, act in the name of a shared global ideology and encourage others to follow their example.
Over the past decade such a chain of linked mass-casualty attacks extended from Norway to to New Zealand. If it becomes harder to coordinate organized terrorism, individual zealots may replace groups, and individual attacks are harder to prevent than group-organized violence. It is difficult, for instance, for the prosecution to prove that a conspiracy exists when a group does the planning, but impossible if the individual was motivated by online manifestoes.