During Tibet's early history it was an independent and often powerful state, but from the 13th century, when it submitted to Mongol rule, until modern times, it has endured long periods of either Chinese control, Chinese influence, or effective autonomy.

In 1904 British Colonel Francis Younghusband led a mission to seize Lhasa and attempt to exclude other foreign powers' influence over Tibet.

But in 1907 Britain and Russia agreed that both parties would deal with Tibet only through China, and China enforced what it saw as its claim on Tibet through a military invasion in 1910.

It withdrew in the midst of a Chinese revolution in 1911, and to all practical purposes Tibet operated as an independent nation from then until the early 1940s.

This was to change dramatically in 1949, when communist Mao Zedong proclaimed the founding of the People's Republic of China and threatened Tibet with 'liberation'.

China led a military assault on Tibet in October 1950, and in April 1951 Tibet's leaders said they were strong-armed into signing a treaty, known as the 'Seventeen Point Agreement', which gave China control over Tibet's external affairs and allowed Chinese military occupation, in return for pledging to safeguard Tibet's political system.

There was widespread open rebellion against Chinese rule within Tibet by 1956, which tipped over into a full uprising in March 1959. Tibetans say that thousands died during the occupation and uprising, but China disputes this.

On the night of 17 March the Dalai Lama fled to northern India. Some 80,000 Tibetans followed over the next few months.

The Chinese government went on to establish the Tibetan Autonomous Region (TAR) in 1965, and in 1966 Tibet was subjected to China's Cultural Revolution, which destroyed a large number of its monasteries and cultural artefacts.

Since the 1980s, Tibet has enjoyed mixed fortunes. People's freedom to practise their religion has been restored, though monks and nuns still often face persecution. But large-scale Han Chinese immigration, Tibetans say, threatens their unique culture.