Because enslaved Africans were known to attack their masters, burn plantation crops, destroy farm equipment and organize insurrections, laws governing their conduct called “slave codes” placed severe limits on when they were allowed to congregate. The very idea of Africans meeting in groups of three or more for purposes other than religious worship terrified the slave-owning class.

As the ACLU of Michigan looks back this week on the legacy of Dr. Martin Luther King, we think it’s important to also give a nod to the tradition of black mass mobilization—a tool King wielded to significant effect—and its significance today.

Notwithstanding the eventual abolition of slavery, the fear of mobilized people of African-descent endured. In 1941, civil rights hero A. Philip Randolph succeeded in urging President Franklin Roosevelt to take affirmative steps toward opening up defense plant jobs to blacks by merely threatening to bring thousands of black people to Washington, D.C. to demonstrate. Because of the concession, that march did not occur.

But 22 years later, in the period leading up to perhaps the best-known march on Washington, the federal government was fit to be tied. Fearing violence the Kennedy administration had 4,000 army troops on standby; they closed all liquor stores, and they arranged for local police, FBI agents and army intelligence agents to infiltrate the crowds. In the years following the 1963 demonstration, increasing numbers of social activists began to use large demonstrations as a tactic, and law enforcement began to study and refine techniques for handling a form of protest that became a permanent part of American political culture.

Not surprisingly, as march organizers began to secure permits, have meetings with law enforcement to coordinate the events and get insurance coverage, the fears of government subsided. Black people in the streets weren’t scary anymore, and the powers that be not only had no worries about these demonstrations, they actually regarded them as useful pressure valves for the release of black anger. In the process, the effectiveness of public demonstrations was lost because, in order for power to concede anything, it must not only receive a demand, but also those with power must be taken well out of their comfort zone.

Then, Ferguson happened. It was unpredictable, uncontained, uncontrolled by government and it became the genesis of a new movement. Law enforcement and government were thrown for a loop, and activists made the world take notice. Sustaining the success of that historical moment will require that organizers remain mindful of the fact that the movement’s leverage rests largely on its independence, capacity to disrupt the status quo, and willingness to make those in power uncomfortable if not downright worried about what the movement will do next.

There are still some marginal benefits to “picnic in the park” type demonstrations—but mobilizing for real change demands an attitude and approach that channels the spirit of those enslaved Africans who identified those things that were most precious to their masters and then attacked them without mercy.

The 21st century descendants of enslaved Africans need not engage in violence, but they should be strategic and fearless in non-violent mass mobilizations that are calculated to impact the things those in power care the most about.