"The tale of these two clans goes on for centuries, and is as fraught with complications as the history of Japan itself—someday when we are on a long sea-voyage perhaps I will relate more of it. What is important is that copper and then silver were discovered in the rocky up-lands. This was about two hundred years ago, at a time when the shogun turned his back on the affairs of the world and went into retirement, and Japan ceased being a unified country for a very long time—like Germany today. All power fled from Kyoto to the provinces, and each part of the country was controlled by a lord called a daimyo, something like a baron in Germany. These daimyos clashed and strove against each other ceaselessly, like stones on a pebble beach grinding each other. Ones who met with success built castles. Markets and cities formed round their walls. Markets require coins, and so each daimyo began to mint his own currency.