Robinson's major league debut brought an end to approximately sixty years of segregation in professional baseball, known as the baseball color line. After World War II, several other forces were also leading the country toward increased equality for blacks, including their accelerated migration to the North, where their political clout grew, and President Harry Truman's desegregation of the military in 1948. Robinson's breaking of the baseball color line and his professional success symbolized these broader changes and demonstrated that the fight for equality was more than simply a political matter. Civil rights movement leader Martin Luther King Jr. said that he was "a legend and a symbol in his own time", and that he "challenged the dark skies of intolerance and frustration." According to historian Doris Kearns Goodwin, Robinson's "efforts were a monumental step in the civil-rights revolution in America ... accomplishments allowed black and white Americans to be more respectful and open to one another and more appreciative of everyone's abilities."