Video: Next Wal-Mart CEO Faces Challenges Sam Walton Never Saw

As Wal-Mart prepares to anoint the fifth chief executive in its history, the world's largest retailer is grappling with challenges founder Sam Walton never faced. Wal-Mart's board has identified international chief Doug McMillon, 46, and Bill Simon, 53, who runs the U.S. operations, as leading candidates to succeed Chief Executive Officer Mike Duke, according to a person familiar with the situation. While Duke, 63, isn't expected to step down immediately, Wal-Mart may