For Saturday’s No Kings protests, an estimated five million people marched in over 2,000 cities and towns. The marches were a striking display of nonviolent dissent amid an increasingly volatile political environment.

Together with the military deployment in Los Angeles and the military parade that President Trump presided over in Washington, these events showcase how the strategic use or rejection of force could shape months, even years, of mass protest as well as the future of American democracy.

History and research make clear that violence seen as unnecessary — whether from the state or protesters — typically reduces popular support for the political players who use it. The public’s rejection of violence they view as unjustified is consistent — so much so that it often elicits complex strategic games, with movements and the state maneuvering to portray the other as unnecessarily violent. Still, important exceptions exist, and understanding when and why nonviolence wins hearts and minds requires understanding the vast research on the topic.

Cross-national research by Maria Stephan and Erica Chenoweth finds that when states crack down violently on nonviolent protest, it often backfires. Rather than quell dissent, repression can mobilize opposition and erode the government’s legitimacy. Other scholarship suggests that when state officials use excessive force against peaceful protesters — such as when the police commissioner Bull Connor in 1963 blasted civil rights activists with fire hoses in Birmingham, Ala. — the images generated can be particularly effective for movements.

These findings suggest the more force the state uses on peaceful demonstrators, the more the state may inadvertently fuel precisely the kind of mass opposition it seeks to suppress.