The power of the Han Dynasty declined by the end of the second century BC. The last Han emperor, Xian, was forced to abdicate in 220 AD. He was succeeded by one of his generals, Cao Pi, marking the beginning of the Wei Kingdom. This, in turn, led to two other Han generals with imperial pretensions establishing the Wu Kingdom in Nanking and the and Shu Han Kingdom in Szechwan. The leader of each kingdom considered himself Emperor of China, and the three states fought a devastating war against each other for the next sixty years. It is estimated that 40,000,000 people may have died during this period as a result of war, famine, and disease.