You can't escape China in AP World History! It is important in EVERY... SINGLE... PERIOD. The Post-Classical Period is no exception. China experiences its second Golden Age during the Post Classical Period. After centuries of decentralized rule, the SUI DYNASTY emerged and reunited the Empire (and built the Grand Canal). The short-lived SUI DYNASTY gave way to arguably China's greatest Dynasty, THE TANG. After the TANG came the SONG and then... THE MONGOLS! If the Post Classical Period is remembered for Muslims & Mongols; China is a close third. Again... If you think you don't know enough about China, you're probably right. Welcome back, China.