Behind this wave of terror was the Jalisco New Generation Cartel, whose abbreviation in Spanish is C.J.N.G., a sprawling crime mob that traffics cocaine, meth and fentanyl and runs other rackets including oil theft and extortion. After Mexican security forces killed the cartel’s leader, Nemesio Oseguera, on Sunday, cartel operatives unleashed the narco blockades in 20 of Mexico’s 32 states. Its gunmen effectively shut down large swaths of the country, killed at least 25 members of the National Guard and showed the world that Mexico’s cartels are not just a public safety problem but a debilitating national security threat.