They pursue their prey using outboard motors instead of oars and tote rocket-propelled grenades instead of cutlasses. But like their peg-legged predecessors, the pirates of today's headlines--most recently those who hijacked a Japanese cargo ship off the Somali coast on July 20--are economic opportunists exploiting the largely unpatrolled waterways through which 90% of global trade flows.
Pirates have plagued seafarers for millenniums. Homer and Cicero noted incidents involving ancient Greek and Roman mariners, and West Europeans weathered Viking onslaughts during the Middle Ages. In the 16th and 17th centuries, monarchs frustrated by Spain's dominance of the Caribbean commissioned privateers to harass...