Even as Trump’s coming arraignment reflects a different set of circumstances, the response is informed by lessons learned from the Capitol riot and from the challenges posed by the nationwide protests against police violence in 2020. They include the need to deploy forces quickly when threats pop up on social media, and the importance of sharing intelligence among agencies in real time, officials have said. The New York City Police Department, state law enforcement agencies, the Secret Service and the U.S. Marshals Service have been coordinating efforts, while increasing intelligence gathering and mobilization. The police, for instance, sent a stand-ready...