The national student sit-in movement began with the Greensboro sit-ins in North Carolina several months later. Although initiated as a nonviolent campaign which would not respond to white violence, in some locations, including Portsmouth Virginia and Chattanooga, Tennessee, blacks forcefully defended themselves against assaults. Robert F. Williams led a successful sit-in campaign in Monroe where, he reported, no racists dared to attack his group because it was well-known his use of nonviolence was strictly conditional. In Jacksonville, Florida, the local NAACP made preparations to defend nonviolent activists by enlisting a local street gang to respond to any attacks. This led to a citywide clash covered nationally as "Axe-handle Saturday" where dozens of blacks and whites were injured in August 1960. Lunch counters were desegregated in Jacksonville and many other sites of protest in the following months. Doug McAdam cited "Axe-handle Saturday" as an example of the specter of violent crisis that loomed over lunch counter sit-ins generally, finding that the threat of escalating chaos pressured authorities to make concessions.