The Gulf Cartel is one of the oldest and most powerful of Mexico’s criminal groups but has lost territory and influence in recent years to its rivals, including its former enforcer wing, the Zetas. Working with Colombian suppliers, this group moves drugs north from its stronghold in Tamaulipas, and is known to outsource other activities, especially those related to human trafficking, to local “enforcer” gangs. Its one-time boss, Osiel Cardenas Guillen, was considered the country’s most powerful underworld leader at one point, and its enforcers, the Zetas, considered Mexico’s most feared gang.