Investors hate risk. So when one country sinks another’s ship, killing 46 sailors, and threatens “all-out war,” it sounds like a good time to sell, right? Wrong. Political crises sometimes can be a great time to buy. When South Korea released a report on May 19 proving that the North was behind a torpedo attack two months earlier, tensions heightened and stock prices tumbled. But steely-nerved investors swooped in, and those who bought a broad index of South Korean stocks at the low made a 12 percent return in about a week—and it’s still trading roughly 13 percent off this year’s high, making for plenty of upside opportunity.