Today, for the first time in Wal-Mart’s 50-year history, workers at multiple stores are out on strike. Minutes ago, dozens of workers at Southern California stores launched a one-day work stoppage in protest of alleged retaliation against their attempts to organize. In a few hours, they’ll join supporters for a mass rally outside a Pico Rivera, Calif., store. This is the latest – and most dramatic – of the recent escalations in the decades-long struggle between organized labor and the largest private employer in the world.