A week before dozens of Proud Boys helped lead a pro-Trump crowd in a violent assault on the Capitol last year, Enrique Tarrio, the group’s president, and some of his top lieutenants held a crude videoconference. with a handpicked crew. members. The meeting, on December 30, 2020, marked the founding of a special new chapter of the Proud Boys called the Ministry of Self-Defense. The team of several dozen trusted members was intended, Mr. Tarrio told his men, to bring a level of order and professionalism to the group’s upcoming march to Washington on January 6, 2021, which had, by...