John Fleming, executive vice president and chief merchandising officer of Wal-Mart U.S., will leave the company on Aug. 1. The announcement comes four days after Bill Simon’s appointment to replace Eduardo Castro-Wright as president and chief executive officer of Wal-Mart U.S. Both Fleming and Simon, had long been considered one of the rising stars at the $400 billion retailer, the world’s largest. Fleming was appointed chief merchant, the company’s first, in January 2007 a...