Tibet was invaded by peoples liberation army and United Nations was a mute spectator. In fact India didn't do anything and this was the single biggest mistake of Republic of India. Tibet had been in central Chinese control but it was also independent many time. read more
As for the invasion of Tibet, if it weren't for the rebellion of Tibetan landlords in areas OUTSIDE of Tibet, and the subsequent war started by Dalai Lama's CIA army, China would've left the Dalai Lama in power, at least for a few years. read more
When Tibet complained to the United Nations through El Salvador about Chinese invasion in November 1950—after China captured Chamdo (or Qamdo) when Tibet failed to respond by the deadline to China's demand for negotiation--members debated about it but refused to admit the "Tibet Question" into the agenda of the U.N. General Assembly. read more