In summer, dried-up river valleys offered easy invasion routes for horsemen bent on sacking the rich Chinese towns of the plains. And this is why these passes were heavily fortified, even though they had let the rest of the Great Wall fall into ruins. A Mongol army of 100,000 warriors invaded China through this pass north of the capital, Beijing. It is still the main highway where the train and motorway to Beijing pass through the mountains. Genghis Khan halted here in front of the north gate of the Juyongguan(居庸關(guān)) Fortress. The Chinese pierced the ground in front of the gate with spikes to slow down the Mongol hordes, and sealed the great gate of the fortress with iron to prevent it from being opened.
After a month of stalemate and no sign of weakening in the fortress, Genghis Khan decided to outflank it. He sent a team of soldiers through the hills where the Chinese at this stage had not maintained the wall, and came from behind the fort. By the time the Chinese army realized what was happening, it was too late. The Mongols were swarming through the plain, attacking Juyongguan from the rear. They destroyed the north gate, and opened the way to the main army. Foreigners and barbarians now ruled China. It was a bitter lesson that the Chinese would never forget. The successor to Genghis Khan was Kublai Khan(忽必烈) who ruled the largest empire the world has ever known, running from China to the very borders of Europe. And he had no need of a Great Wall, he controlled it all.
This is when the famous traveler Marco Polo visited China and wrote his famous book on his experiences. Many people have wondered why he never once mentioned China's most famous monument, the Great Wall. It's simple: the Great Wall was in such ruins by his time that it wasn't worth mentioning.
Despite his power, Kublai Khan wasn't going to last. The Chinese still viewed their Mongol rulers as invading barbarians. Devastating floods in the Yellow River triggered a popular revolt against their hated foreign rulers, and the Mongols were overthrown. They were replaced by a Chinese dynasty, the Ming, who were determined that the mistakes of the past would not be repeated. These are the descendants of the men who built the wall for the Ming and chased the Mongols out of China. They are proud of their ancestors, men and women, who built and defended the last Great Wall of China. That's why these farmers in a remote village still perform martial arts every morning before heading off to work in the fields
忽必烈(1216-1294, 元世祖, 中國(guó)元朝皇帝, 成吉思汗之孫)
bent on sth: determined to do sth
sack: plunder; loot
outflank: maneuver around and behind the flank of (an opposing force)