Top South Korean officials moved inexorably Friday toward blaming North Korea for the sinking of a Navy ship three weeks ago, in a case in which many see the government's integrity and judgment in the balance. While South Korea’s defense minister warned of “a grave national security issue,” the government clearly hoped to avoid an escalating crisis that might jeopardize economic success as well as the ability of President Lee Myung-bak to govern effectively. The government “keeps saying there will be a firm response,” says Han Sung-joo, a former foreign minister and ambassador to the United States, “but that doesn’t...