Foreign Policy Magazine's roundup of the world's most dangerous gangs in the world.

Mara Salvatrucha (MS-13), United States and Central America

Membership: 70,000 worldwide (60,000 in El Salvador, Honduras, Guatemala, and Mexico, plus 10,000 in 42 U.S. states and Washington, D.C.)

Stronghold: Central America and U.S. suburbs

Known for: elaborate tattoos (which makes ending gang membership almost impossible), suburban bloodshed, and a loose but widespread network of subsidiary groups, perfect for disseminating drugs and brutal violence

Why they’re dangerous: The MS-13 grew out of a posse (mara) of street-tough Salvadorans (Salvatruchas) who fled to Southern California in the 1980s in the wake of El Salvador’s bloody civil war. With each new wave of vulnerable immigrants from Central America, MS-13 grew in strength and breadth, forming a lose cohort of semiautonomous subsidiary gangs across the United States and Central America. Though their hallmark tattoos and violent outbursts dot North America, analysts are still uncertain just how interconnected the maras really are. In the United States, the strongest maras are based in Southern California, the northeast, and the mid-Atlantic, including the Washington, D.C., metro area. Just last spring, Salvatruchas hacked away at a rival gang member in the D.C. suburb of Alexandria, Virginia. But U.S. maras are nothing compared with their counterparts further south. Fueled by gang members deported from the States, maras in El Salvador, Honduras, and Guatemala terrorize police and residents in hundreds of communities across the region.