When his subjects weren't peaceful, Genghis Khan had them flogged. In this illustration, he watches on while someone else does the dirty work.

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The Mongols: Fearsome Hordes, or Bringers of Peace?

A thousand years after the Pax Romana, another era of international peace was established. Throughout the Eurasian continent, an empire arose that had advanced technology and a strong economy and protected thousands of miles of trade routes. In fact, it was this empire that enabled Marco Polo to travel by land from his home in Italy to China. Yes, believe it or not, it was the fearsome Genghis Khan, unifier of the Mongol hordes, who established the largest -- and one of the most peaceful -- kingdoms in history.

Today, we associate Genghis Khan and his successors with fearsome battle tactics and ruthless invasions. There's no question that his military strategies resulted in the deaths of countless people; by employing armies of archers on horseback, Genghis Khan was able to out-fight and outpace nearly any foe he encountered.

Within a matter of years, he'd taken control of the Mongol tribes, expanded their territory into an empire millions of square miles in area and managed the Silk Road trading route that linked Europe and Asia. At first glance, these accomplishments might not seem to indicate a peaceful time. But once the Mongolian empire was firmly established, life for its citizens seems to have actually improved.

One innovation the Mongols established was a postal system -- the first of its kind to connect the East and the West. The Mongolian government set up relay stations throughout their territories; each station was equipped with fresh horses and supplies and was maintained by the local population. This system allowed information to travel quickly and efficiently throughout the empire. Strict laws protected civilian property and travel; a famous legend purports that a woman could carry a sack of gold from one end of the empire to the other without fear of attack. Trade with other nations was very important to the Mongols, and that, too, was heavily guarded by law [source: New World Encyclopedia].

But do those innovations and prosperity outweigh the destruction wrought by the expansion of the Mongolian Empire? Enemies of the government were all but annihilated, and any internal resistance was dealt with in a swift and brutal manner. Even though the legacy of the Mongols is still evident today, they didn't establish the most peaceful era in history.

Now that we've eliminated the Romans and the Mongols, who's left?