The organization's origins go back to the late 1990s as the elite private security apparatus of the Gulf Cartel. In an effort to outdo their rivals, the Gulf Cartel formed the Zetas out of a core of at least 31 deserters of the Mexican Special Forces.
The formal military training of the early Zetas, along with their penchant for committing bloody and audacious acts such as beheadings and petrol bomb attacks, have led the DEA and the Mexican authorities to declare the Zetas to be their No. 1 enemy within Mexico.
In 2010, following the arrests and death of Zetas and Gulf Cartel leaders, the Zetas violently split from the Gulf Cartel, of which they had previously served as a military wing. The Zetas followed the split with a string of high-profile attacks against DEA and US immigration agents.
Today, the group has fractured somewhat under joint attacks from the Sinaloa and the Mexican government, but they have spread into Guatemala and diversified their criminal enterprises into child prostitution and oil theft.