Forty years ago, Chinese communist chairman Mao Zedong launched the Great Proletarian Cultural Revolution. It's an unpleasant anniversary that official Beijing will not celebrate and most Chinese would rather forget.

Mao's objective: to purge the party of its moderate, pragmatic faction, which he said was leading China away from Marxism and toward capitalism and to make himself unassailable leader.

The bloody, chaotic decade between 1966 and 1976 which ensued was among the most violent, divisive and shameful in China's long, illustrious history.