Documents submitted as part of a 2015 US National Labor Relations Board investigation show that Walmart, long known to be hostile to unions, spied on and retaliated against a group of employees who sought higher wages, more full-time jobs, and predictable schedules. In combating the group, who called themselves the Organization United for Respect at Walmart (OUR Walmart), Walmart hired an intelligence-gathering service from Lockheed Martin, contacted the FBI, and set up an internal Delta team…