Why did China conquer Tibet?

The conquering of Tibet by Communist China was a catastrophic event in several ways. The invasion in 1950 put the land into years of turmoil and finally the Tibetan Government was completely overthrown. Finally, the Dalai Lama along with about 100,000 people had to leave the country because their lives were in danger. It is also reported that more than one million people of Tibet were killed.

Tibet is actually a large country and in land mass would be considered the 10th largest nation. The land also has a rich supply of natural resources and strategically borders India. China claims that Tibet has been part of China for over 800 years, but Tibetans assert that they have been an independent nation for over 2,000 years.