Feola (defendant) and four other individuals, Alsondo, Rosa, and Farr, (collectively Defendants) arranged for a sale of heroin to buyers who turned out to be undercover federal agents. However, Defendants planned to substitute sugar for the heroin and simply take the money the agents had brought to purchase the drugs in the event the agents became suspicious. One agent did become suspicious and drew his revolver in time to prevent an assault on another agent. Defendants were charged the substantive crime of assault on a federal officer in violation of 18 U.S.C. § 111 and conspiracy to commit that substantive crime, in violation of 18 U.S.C. § 371. Defendants were convicted on both counts in the district court and they appealed. The U.S. Court of Appeals for the Second Circuit affirmed the convictions on the substantive count, but reversed the conspiracy convictions. The U.S. Supreme Court granted certiorari to review.