Book excerpt: Ever since Korea was first divided at the end of World War II, the tension between its northern and southern halves has riveted—and threatened to embroil—the rest of the world. In this landmark history, now thoroughly revised and updated in conjunction with Korea expert Robert Carlin, veteran journalist Don Oberdorfer grippingly describes how a historically homogenous people became locked in a perpetual struggle for supremacy—and how they might yet be reconciled.