Among the far-right groups whose members are suspected of planning the Jan. 6 attack on the U.S. Capitol are the Proud Boys. In March, the Federal Bureau of Investigation’s director told the Senate Judiciary Committee that he “absolutely” wished the agency had penetrated the group beforehand, or knew its plans. “I do not consider what happened on January 6th to be an acceptable result,” Director Christopher Wray said. “We are focused very, very hard on how can we get better sources, better information, better analysis.” The FBI had deeper insight into the group than Wray disclosed, however. Bureau agents maintained...