In Jack Riley’s new memoir, Drug Warrior (February 19, Hachette Books), the former Drug Enforcement Administration agent (who eventually became second in command at the DEA) traces his two-decade hunt for Joaquín Guzmán Loera, the notorious Sinaloa drug cartel leader known as El Chapo, much of which was centered in Chicago. Here are five things you’ll learn.

1 Riley was behind naming El Chapo Chicago’s public enemy No. 1. In order to link Guzmán to the city’s escalating violence, Riley persuaded the Chicago Crime Commission to give that designation to the Sinaloa cartel leader in 2013. (The last time it had been used was for Al Capone.) “The suits in Washington didn’t like it,” Riley writes, “but I felt we had to make a statement.”

2 Garry McCarthy wasn’t interested in the big fish. Riley struggled to get McCarthy, who was then Chicago’s police superintendent, to prioritize cooperation among departments. “I told him we needed to focus on the big targets — the cartels and the gangsters. But he was happy simply picking up the dime-bag dealer on the corner.”

3 The Sinaloa cartel used a fake Illinois company to move drugs into Chicago. The DEA tracked a shipment of “titanium pigments” imported from Mexico by a fictitious company called Earth Minerals Corp., supposedly based in tiny suburban Rockdale. When the train pulled into Chicago Heights, agents seized what turned out to be 11 tons of marijuana.

4 Twin brothers from Chicago helped bring down El Chapo. Discreet and businesslike, Pedro and Margarito Flores had, by age 25, moved an estimated $1.8 billion in drugs through the city. They flipped, and their taping of a deal with Guzmán — a rare recording of the boss in action — was pivotal in the case against the drug lord.

5 Riley really, really hates Sean Penn. DEA agents and the Mexican marines had to abort a takedown of Guzmán after they learned the actor was at his safe house to interview him for Rolling Stone. “It was all because of this moron.”