Los Zetas
Tamaulipas was mostly spared from the violence until early 2010, when the Gulf Cartel's enforcers, Los Zetas, split from and turned against the Gulf Cartel, sparking a bloody turf war. When the hostilities began, the Gulf organization joined forces with its former rivals, the Sinaloa Cartel and La Familia Michoacana, aiming to take out Los Zetas. Consequently, Los Zetas allied with the Juárez Cartel, the Beltrán-Leyva Cartel and the Tijuana Cartel.