Question: In what year did this criminal group, formed by former soldiers of the Mexican Armed Forces and Founded by Nabor Vargas Garcia, break away from their former employer and form their own criminal organization?
Sentence (from "Los Zetas"): The origins of Los Zetas date back to the late 1990s when commandos of the Mexican Army deserted their ranks and began working as the enforcement arm of the Gulf Cartel.
Relevant evidence: No