On 7 March 1965, a peaceful civil rights demonstration in Selma, Alabama was brutally attacked by white police officers. Martin Luther King Jr. had organized the effort but did not personally lead the march which was supposed to go from Selma to Montgomery. The pretext for the protest was voter registration discrimination that still predominated in the wake of the Civil Rights Act. The crackdown (with tear gas and truncheons) on the 1500 peaceful demonstrators prompted President Johnson to pass the Voting Rights Act, another measure designed to ameliorate discrimination and prevention of voter registration.
Richert, Lucas Paul. "Civil Rights march in Selma, Alabama, attacked by police". The Literary Encyclopedia. First published 01 October 2008
[http://www.litencyc.com/php/stopics.php?rec=true&UID=3441, accessed 23 March 2017.]