The first pages of a book like this are usually the last ones written, so it feels right to start (and end) it here in Maré. My earliest visits to this sprawling collection of favelas (slums) in 2003 opened my eyes to the absurdity of Rio's drug war, with its home-grown drug syndicates locked in a decades-long militarized conflict with brutal and corrupt police. It was here, talking with locals, that I began to understand the intertwined dynamics of violence and bribery driving and sustaining this conflict. It was here that I saw first-hand the capacity of enlightened state policy to radically transform those dynamics, mostly for the better. And it is here that I now see the tragic fragility of such policies and the terrifying resilience of this conflict.

Rio's residents have been cynically predicting for years that the “Paci- fication” strategy—a novel approach to policing that, since its rollout in 2008, vastly curtailed violence while re-establishing state control in some 200 favelas—would be dismantled once the 2016 Olympics ended. As I write, the Olympic flame is still burning, and many of the city's largest favelas are still Pacified, but here in Maré, the end of Pacification is in plain view. As we turn off Avenida Brasil at the entrance to the Nova Holanda neighborhood, gone is the army soldier who stood guard on my previous visit in 2015; in his place stands a teenager holding an AR-15 automatic rifle almost as long as he is tall, next to a makeshift barrier made from scrap I-beams. He looks us over through the windows we perfunctorily roll down, then waves us on with the barrel of his weapon. When our car cannot fit between the I-beams, he shouts and some nearby kids come and clear a path for us. A few blocks down the bustling street, on a busy corner, more armed youths stand around a large table stacked with small packages labeled “Crack Nova Holanda, $2.”

Except for the crack—drug syndicates used to prohibit its sale but eventually gave up—and the nifty new printed labels, the scene is indistinguishable from my earliest visits to Maré.