Mongols and Yuan Dynasty
The Mongols were nomadic conquerors of China, pouring forth from the steppes of Central Asia. Their lifestyle made them tough and skilled when it came to life outdoors, meaning they would be difficult to overcome in battle. They created their empire with ease.
The top dogs in this empire where known as khans, or chiefs, who were the leaders of the clans. One of them would rise, conquering all other khans to become Gengis Khan, or Universal Ruler. United, the Mongols would form the military power that would conquer nearly all of Asia. Their methods, while brutal, were very efficient.
After Genghis's death, however, his lands would decide again. His heirs would divide the empire into four sections, called khanates. One leader would still rule as the Great Khan, though. Under the heirs, the Mongols continued expanding their borders with horrible force. Their violent ways made people think of them as barbarians, no doubt.
This was not the case, however. In fact. Under Mongolian rule life was so peaceful that historians would dub it the Pax Mongolia, or Mongol Peace. All of the areas would be culturally untouched, as the Mongols would allow them to retain their beliefs and practices, as well as keep their leaders provided they payed tribute to their conquerors. The Mongols would even accept some of the cultures' aspects as their own, such as inheriting Islam as on of their religions. They also protected trade routes, allowing everything from China to make its way west. Sadly, a horrible disease known as the Black Death would spread just the same.
Here is a bit more on the Mongols' success.
One of the heirs of Genghis's Khan, Kublai Khan, wanted to fulfill his mission to gain all of China. He would do so by conquering the south, ruled by the Song Dynasty. It would take years, but the last Song ruler would die and allow Kublai Khan to create the Yuan Dynasty. With himself as emperor, of course.
A lot of changes occurred when he was emperor, both culturally and physically. That is, the new empire would adopt Chinese customs as well as a Chinese name, Yuan. This was simply to ease the minds of the new citizens, because Kublai Khan would forbid the blending of cultures by banning marriage between Mongols and the Chinese. In fact, they weren't really allowed to be friends. The Chinese had different laws and taxes, and were not allowed their own weapons or service in the army. They had virtually no power in the government. Change would also occur when the capital was moved near present day Beijing. The Grand Canal was also expanded, making it even easier to transport goods between north and south. Trade in itself was improved as well. With safe roads and new ships, foreign trade took a big step forward under the Yuan Dynasty.
The dynasty would end, but not without a fight. Many fights, in fact. Fights they would...lose. Which is why the dynasty ended. Kublai Khan would send forces to Southeast Asia, only to come crawling back home after a bad loss. He would also embarrass himself by trying twice to invade Japan, only to be weakened twice by terrible storms. It makes you wonder if there was some divine force protecting the islands of Japan. The people at the time certainly thought so. Everything would go wrong. Kublai Khan himself would die, and his successors simply weren't cut out for ruling his empire. And so, with the economy in shambles thanks to big spending on public works, and an entire people made restless by Kublai Khan's mistreatment, a rebellion broke out. The remaining Mongols would flee, leaving China once again up for grabs.
Marco Polo wrote a lot about his experience in China during this time period. Let's learn a little more about Polo himself, or the things he wrote down.