Beginning with the imprisonment of Mexican drug kingpin Miguel Angel Felix Gallardo in 1989, and the division of his criminal empire into the Sinaloa and Tijuana cartels, the cartel cowboys' history has been a bloody one. Former lieutenants and cousins of Felix Gallardo, the Arellano Felix brothers built their Tijuana DTO into a major billion dollar organization. They formed alliances with street and prison gangs in the U.S., including the Mexican Mafia.
Their chief rivals were the Vicente Carrillo Fuentes DTO, or Juarez Cartel, and Caro Quintero's DTO, which controlled the Nogales gate. The three DTOs controlled all three major entry points. When Quintero was imprisoned, the Nogales gate was up for grabs.
Joaquin "Chapo" (Shorty) Guzman came from Sinaloa with almost nothing. He escaped from prison in 2001 and formed an alliance with Ismael "El Mayor" (the Elder) Zambada, who inherited the Juarez Cartel when Vicente Carrillo Fuentes was arrested. Now the Gulf and Tijuana cartels have formed an alliance against Guzman. He has managed to maintain the trust of the Colombian narcotics sources, and is brutally efficient in murder. Police officers, prosecutors, journalists, and whole families have been slaughtered in the drug wars.
Whole Mexican Police and Army units, both state and federal, have gone over to the dark side. Many police officers supplemented their income in the long accepted Mexican practices of taking bribes, or mordeda (the bite), robbing drug dealers, and extorting wealthy families. When Mexico cleans them out of the Police Units they cross the border and continue to rob and extort their own people on this side.
Some Special Forces units of the Mexican Army also have deserted and sold their souls to the DTOs. The unit known as Zeta ("Z"), after its former radio call sign, is one of these units killing for the cartels along both sides of the border.