Two years ago, a California aluminum executive commissioned a pilot to fly over the Mexican town of San José Iturbide, at the foot of the Sierra Gorda mountains, and snap aerial photos of a remote desert factory. He made a startling discovery. Nearly one million metric tons of aluminum sat neatly stacked behind a fortress of barbed-wire fences. The stockpile, worth some $2 billion and representing roughly 6% of the world’s total inventory—enough to churn out 2.2 million Ford F-150s or 77 billion beer cans—quickly became an obsession for the U.S. aluminum industry. Now it is a new source of tension in U.S.-Chinese trade relations. U.S. executives contend that the mysterious cache was part of a brazen scheme by one of China’s richest men to game the global trade system. The Wall Street Journal reports Related: