Rio de Janeiro woke up with quite a hangover from this year’s carnival. On Friday, two days after the end of Brazil’s largest party, the federal government issued a decree placing the armed forces in charge of all security agencies. This was a reaction to skyrocketing criminal violence, and the first case of military intervention since the end of the military regime in 1985. Yet, Rio has been plagued by organized crime, drug trafficking and violence for decades. What changed?