Originally a mechanic in Matamoros, Tamaulipas, he entered the cartel by killing Juan García Abrego's friend and competitor Salvador Gómez, after the former's arrest in 1996.

As confrontations with rival groups heated up, Osiel Cárdenas sought and recruited over 30 deserters from the Grupo Aeromóvil de Fuerzas Especiales to form the cartel's armed wing.

[10] Hugo Baldomero Medina Garza, known as El Señor de los Tráilers, is considered one of the most important members of the Gulf Cartel.

After his imprisonment a short time later, Jorge Madrazo Cuéllar created the National Public Security System (SNSP), to fight the drug cartels along the U.S-Mexico border.

[21] Among the original defectors were Jaime González Durán,[22] Jesús Enrique Rejón Aguilar,[23] and Heriberto Lazcano,[24] who was killed in 2012 while he was the supreme leader of Los Zetas.

[28] Once Cárdenas consolidated his position and supremacy, he expanded the responsibilities of Los Zetas, and as years passed, they became much more important to the Gulf Cartel.

They began to organize kidnappings,[29] impose taxes, collect debts, operate protection racket,[30] control the extortion business,[31] secure cocaine supply and trafficking routes known as plazas (zones) and execute its foes, often with grotesque savagery.

[34] The death of Arturo Guzmán Decena (2002),[35] and the capture of Rogelio González Pizaña (2004),[36] the second-in-line, marked the opportunity for Heriberto Lazcano to take charge of Los Zetas.

[38][39] On 9 November 1999, two U.S. agents from the Drug Enforcement Administration (DEA) and Federal Bureau of Investigation (FBI) were threatened at gunpoint by Cárdenas and approximately fifteen of his henchmen in Matamoros.

Prior to the standoff, he was regarded as a minor player in the international drug trade, but this incident grew his reputation and made him one of the most-wanted criminals.

[43] On 1 June 2001, the U.S. Department of the Treasury sanctioned Cárdenas under the Kingpin Act, for his involvement in drug trafficking along with eleven other international criminals.

[44] The act prohibited U.S. citizens and companies from conducting any kind of business activity with him, and virtually froze all his assets in the U.S.[45] Osiel Cárdenas Guillén was captured in the city of Matamoros, on 14 March 2003 in a shootout between the Mexican military and Gulf Cartel gunmen.

[50] He was extradited in 2007 to the United States, where he was sentenced to 25 years in a prison in Houston for money laundering, drug trafficking, homicide and death threats to U.S. federal agents.

[51] Reports from the PGR and El Universal state that while in prison, Osiel Cárdenas and Benjamín Arellano Félix, from the Tijuana Cartel, formed an alliance.

Moreover, through handwritten notes, Osiel Cárdenas gave orders on the movement of drugs in Mexico and into the United States, approved executions, and signed forms to allow the purchase of police forces.

[61] The standoff the two agents had with the drug lord in 1999 in the city of Matamoros led to the U.S. indicting Cárdenas and pressuring the Mexican government to capture him.