History’s greatest mysteries: why did Mao’s chosen successor flee China?

Fifty years ago, in September 1971, Lin Biao boarded a flight out of the country, only to crash in the Mongolian desert shortly afterwards. Was this the result of an aborted coup on Lin’s part? And where exactly was his plane heading? In the latest in our series on history’s biggest conundrums, historian Rana Mitter answers these questions and more about the mysterious “Lin Biao incident”.