Complex sentence: The Mongol Yuan dynasty (1271--1368) ruled all of China for about a century, and dominated Northern China for more than 140 years, since the time when the Jurchen Jin dynasty was annihilated.
Split into simpler sentences: The Mongol Yuan dynasty (1271--1368) ruled all of China for about a century. However, the Mongols dominated North China for more than 140 years, starting from the time when the Jurchen Jin dynasty was annihilated.