Z-40, a former Mexican special forces operative, was one of the first to defect and join the Gulf Cartel’s security arm, the Zetas. When Zetas commander Arturo Guzman Decena was killed in 2002, he rose through the ranks. In 2006, he was stationed as the "plaza" boss in Nuevo Laredo, the Zetas’ longtime base of operations. Near 2007, he was sent to Veracruz following the death of a high-ranking member of the group. He took control of that drug trafficking corridor, while simultaneously taking over other illicit industries such as trade in pirated DVDs and CDs, and human trafficking. He’s also thought to run the Zetas' operations in Guatemala, where the group has established bases in the northern states of Peten and Alta Verapaz.
In July 2012, the Zetas reportedly split into two factions, one side headed by Z-40, the other by Heriberto Lazcano, alias "Z-3." The rival capos each accused the other of betrayal and became embroiled in a bitter and violent power struggle. In October 2012, Mexican security forces reported shooting and killing Z-3, leaving Z-40 as the most senior Zetas commander. However, with the group increasingly resembling a fractured and decentralized network with cells operating independently, it is unlikely Z-40 will be able to assert his authority over what remains of the organization. In October 2012, a Zetas splinter group comprised of opponents of Z-40 announced they had formed a new group, Los Legionarios (the Legionaries), with the express purpose of waging war against Z-40 and his organization.