Entonces: Mara Salvatrucha (MS 13)

During the 1980s, the Central American nation of El Salvador was torn apart by a long and horrifying civil war. Over 75,000 men women and children were killed with one million more fleeing to the United States as refugees. Many of the refugees settled in Los Angeles.

Like Italian, Irish and Jewish immigrants before them, a few of the younger refugees formed gangs. Because some of these gang members served as soldiers in El Salvador's bloody civil war, their gang, Mara Salvatrucha 13 or MS 13, soon became notorious for acts of violence. As the gang's reputation grew, it attracted new recruits from Central America as well as the attention of Los Angeles law enforcement.

In the early 1990s, the U.S. began deporting members of MS 13 back to El Salvador, Honduras and Guatemala. But Central America was unprepared for these U.S.-bred gangs. Against a backdrop of violence and deprivation, MS 13 quickly grew in numbers, ferocity and reach. By the late 1990s, Central American chapters of MS 13 were feeding back into the U.S., prompting one FBI official to remark: "They're deported from here, they start their post graduate studies down there, and then they bounce back to the U.S.”

Entonces: Rather than weakening MS 13, the deportations of its LA-based members may have helped the gang become a transnational criminal enterprise.