William J. Bratton has been appointed the 42nd police commissioner of the City of New York by Mayor Bill de Blasio, the second time he has held the post. Commissioner Bratton established an international reputation for re-engineering police departments and fighting crime in the 1990s. As Chief of the New York City Transit Police, Boston Police Commissioner, and in his first term as New York City Police Commissioner, he revitalized morale and cut crime in all three posts, achieving the largest crime declines in New York City’s history. At the NYPD in 1994 and 1995, he led the development of Compstat, the internationally acclaimed command accountability system now in use by police departments nationwide. As Los Angeles Police Chief from 2002 to 2009 and in a city known for its entrenched gang culture and youth violence, he brought crime to historically low levels, greatly improved race relations, and reached out to young people with a range of innovative police programs. He is the only person ever to lead the police agencies of the nation’s two largest cities.