As can be seen in The HIstory of Tibet entry in Wikipedia, Tibet was sovereign without contest until 1901. The Chinese have asserted sovereignty over it since then, and have enforced it with brute force since the 1950's, in part to a British management policy which lost Tibet as a protected satellite.

Culturally, the Chinese have no real interest I can identify in Tibet -- although it was overrun by Mongols back in the middle ages, it posed no threat to China in the 19th, 20th or 21st centuries. I do not know of any great wealth in natural resources it possesses, or any great strategic interest by reason of its location; so I am at a loss to understand why China elected to simply grab it. I am sure I am being quite ignorant about the larger picture, and would welcome enlightenment as to what the Chinese motive is for grasping and holding Tibet.

A