Two days after George Floyd died, the police chief of Minneapolis called the mayor around dinnertime. He needed help. What had begun as peaceful protests outside the Third Police Precinct was turning into mayhem. “He said: ‘The Target is getting looted. We are not going to be able to handle this on our own,’” recalled Mayor Jacob Frey, who called Gov. Tim Walz and asked for the National Guard. The governor said he would consider the request. Afterward, he expressed surprise that city leaders did not seem to have a plan for where they wanted the soldiers to go. As...