 The police force of the city was overwhelmingly white and the black population resented this.In the early 1940s, Detroit's population reached more than 2 million, absorbing more than 400,000 whites and some 50,000 black migrants, mostly from the American South, where racial segregation was enforced by law.The more recent African Americans were part of the second wave of the black Great Migration, joining 150,000 blacks already in the city.