The head of the Chicago Police Department has announced that he will retire after a short tenure leading the nation’s second-largest police force. Chicago Police Superintendent Larry Snelling took the reins of the department three years ago as it was dealing with a mixed bag of crime. He touted the need for innovation and increasing trust between police and the community, as well as finding ways to tamp down violent crime. Snelling said Wednesday that he will retire on July 15. The superintendent’s job is a notoriously difficult one. Many past heads of Chicago police have lasted only a few years.