Two top-ranking figures within Mexico’s powerful Sinaloa cartel were arrested by U.S. authorities in Texas on Thursday, swinging a blow to the criminal gang responsible for supplying more fentanyl into the United States than any other.

       Ismael “El Mayo” Zambada was an elusive Sinaloa kingpin who evaded capture for decades. Joaquín Guzmán López is a son of famed drug lord Joaquín “El Chapo” Guzmán, with whom he shares a name, and is accused of overseeing a network of methamphetamine labs across Mexico’s northwestern Sinaloa state. Both men were sought by U.S. authorities for drug trafficking.

       Mexican authorities said they were not informed about the operation to capture either man until after they were flown to the United States on a private plane that took off from Mexico’s Sonora state.

       Here’s what to know.