During the second half of the 1960s the civil rights movement became a victim of its own success and of powerful historical forces beyond its control. The destruction of the southern caste system, well advanced by late 1965 as a result of the coalition's multi-pronged strategy, did not lead to complacency. Serious urban riots in cities as far apart as Los Angeles, Chicago and Detroit made it clear that racism and poverty afflicted Mrican Americans throughout the country and not just the South. The urgent need to redefine the movement in order to ensure that non-southern blacks, particularly urban black youth, did not fall prey to despair intensified the ongoing internal debate over goals and tactics. While the more conservative civil rights organisations maintained close ties to the high-spending administration of Lyndon Johnson and SNCC and CORE embraced black separatism, Martin Luther King endeavoured to shore up the centre by making nonviolent direct action relevant to the rapidly changing situation. Even though the SCLC's ambitious attempt to deploy the tactics of the southern movement against de facto segregation in Chicago ended in failure, King retained his faith in nonviolence until his tragic death in Memphis in April 1968. By this stage the intensification of US military intervention in southeast Asia had contributed further to the decline of the civil rights coalition as a cohesive national force. Significantly, however, neither the Vietnam War nor the growth of Black Power put a stop to civil rights activity at the local level. Aided by federal anti-poverty programmes, revivified NAACP branches, and grass-roots voters' leagues emboldened by passage of the Voting Rights Act, black and white activists worked to ensure that the movement left a rich legacy for the future.