"No quarter. Raise the black flag." Enrique Tarrio is raging online about President Joe Biden's election victory. It's November 2020, a couple of months before the January 6 insurrection. But Tarrio isn't just an angry Donald Trump supporter posting on the internet. He's the leader of the right-wing Proud Boys group with perhaps thousands of members ultimately reporting to him. He wanted Mr Trump to remain in office, warning of a second civil war. So he and others hatched a plan, one that culminated in the storming of the Capitol on 6 January 2021. A series of documents and messages,...