Even in Brazil, where homicides are really common, Rio de Janeiro’s crime rate is stunning. It is now impossible not to notice that the city’s Police Pacification Units (UPP), once a much-vaunted anti-violence force, have all but collapsed. Launched nine years ago, the UPP program stationed some 9,500 officers in some 37 favelas, serving nearly 780,000 people. This new model, which included components of successful community policing initiatives in Los Angeles and Medellin sought to end violent confrontations between rival gangs, and between police and gangs, by getting weapons out of the favelas and maintaining a permanent police presence.