More than 2,000 years ago, a scholar at the king's court in northern India composed a seminal document known as the "Arthashastra." It was a lesson on statecraft and was subtle enough that the man himself, Kautilya, is sometimes referred to as the Indian Machiavelli. One of the document's key takeaways was this: "Your neighbor is your natural enemy and the neighbor's neighbor is your friend." Today, whether they have read his works or not, Kautilya's Indian descendants are still following his advice: As neighboring China's growing influence causes increasing concern, India is reaching out to forge new links with its neighbor's neighbor, Japan....