From 206 B.C. to A.D. 221, the Han Dynasty saw advancements in technology, philosophy and trade. However, internal and external influences caused the collapse of the Han Dynasty in the year A.D. 221. The reasons for this Chinese dynasty's collapse range from apathetic rulers to aggression from outside hordes. As a result of its collapse, China was divided into the Three Kingdoms and would not reunite for another 400 years.
Internally, the Han Dynasty started to fall apart when it was ruled by emperors who ruled for their own amusement. The quest for power among scholars and generals led to massacres within the palace.
The economy took a downward spiral when tax revenue hit a low point. The scholars had ruled themselves exempt from taxation, and peasants evaded tax collectors by running into the countryside. The lack of tax money led to a depleted military fund.
With a weakened military budget, the army was not well equipped to defend itself against outside threats. Raids by nomadic peoples, such as the Mongols, were commonplace in China during that era. The Han government did not have the necessary resources to pay off every nomadic warlord it encountered. Ultimately, the Sino-Xiongnu Wars of 133 B.C. to A.D. 89 led to the destabilization of the Han government.