In April 2014, two months before the start of the World Cup, 2,500 Brazilian Army and Marine soldiers occupied Complexo da Maré. They would stay there for the next fifteen months. The occupation of Maré was the culmination of Rio’s once-heralded Police Pacification Units, a public security program intended to recapture the state’s monopoly of violence from drug-trafficking gangs in hundreds of favelas throughout the city. This chapter begins by tracing the confluence of factors which led to the Brazilian military’s intervention. A mix of participant observations, interviews, and newspaper accounts then document the military’s arrival and their various operations and activities to combat gangs and gain the support of the local population. The chapter proceeds to analyze how and why each of Maré’s gangs responded differently to the challenges of occupation, arguing that the military lacked the capacity to fully expel or dismantle them though their presence shifted the dynamics of rival competition and threat, which produced the divergent gang responses observed.