Why did Mao start the cultural revolution (1966) ?

Mao Zedong launched what became known as the Cultural Revolution in order to reassert his authority over the Chinese government. Believing that current Communist leaders were taking the party, and China itself, in the wrong direction, Mao called on the nation’s youth to purge the "impure" elements of Chinese society and revive the revolutionary spirit that had led to victory in the civil war 20 decades earlier and the formation of the People’s Republic of China.