The case of Tibet shows that mistakes once made cannot be rectified. In this the blunders committed by Jwaharlal Nehru, India's prime minister( 1947-64) stand out, but for his inaction in the fifties of the last century the present state of affair where China holds all the aces would not have happened.
China has long coveted Tibet, but at the beginning of the 20th century the British had become the most powerful nation in Asia. This had an effect and Tibet could have a degree of independence from the Chinese. The British influence in Tibet came the hard way after a military campaign by general YoungHusband in 1903-04. The British Indian army occupied Lhasa and the Dalai Lama fled to Sinkiang.
British influence in Tibet grew after that and in 1913, the British called a tripartite conference in Simla which was attended by the representatives of China and Tibet. The conference recognized Tibet as an independent country and also demarcated the boundary between India and Tibet. The agreement gave the British the right to maintain troops in Tibet. The agreement was only initialed by the Chinese representative and not signed. However Tibet became a de-facto independent state and in 1941 even set up its own foreign office.
The British left in 1947 and India under Nehru inherited the British legacy. This was an excellent time to consolidate Indian influence in Tibet, but Nehru with his notion of 'imperialism' withdrew the Indian troops from Tibet. This was a colossal blunder and 2 years later in 1950, 80,000 troops of the PLA( Peoples Liberation Army) attacked Tibet. The Tibet army was routed and appealed to India. Sardar Patel the indian Home minister wanted the Indian army to intervene, but he was a sick man having suffered a heart attack and Nehru decided not to do anything. In fact he recognized Chinese suzerainty over Tibet and only conceded autonomy for it. This was a blunder as the Chinese made the Dalai Lama sign on the dotted line and annexed Tibet as a "autonomous region of China".
Nehru assumed that the Chinese would be grateful to India and propounded the principles of Panch Sheel. But he was not aware about the thinking of Mao tse Tung , who after having fought a war for close to 2 decades had no time for the philosophy of Nehru. He set about the destruction of Tibet culture and shut the Indian consulate in Lhasa. Indian's were debarred from entering Tibet. Suddenly Nehru was faced with a piquant situation and he realized that he had no cards to play on Tibet.
The Tibet people revolted in 1959 and the PLA shot thousands of them in Lhasa and other places. Tibetan nuns were captured from the monasteries and forcibly married to Chinese soldiers or simply raped repeatedly. At that time China was not as strong as today, but Nehru again spurned a golden opportunity to have a say in Tibet. He ruled out military intervention. Worse he left the Aksai Chin area ( 30,000 sq miles) without an administration and the Chinese filled the lacuna and occupied it.
In 1959, the Chinese made a devious plan to kidnap the dalai Lama and take him to China. In case he resisted he was to be executed. The plan leaked to the Dalai Lama, then a young lad of 16 years. His advisors convinced him to escape from the Potala palace to India. The Dalai with his entourage left Lhasa disguised as a common soldier and after a 13 day trek crossed to India. For once Nehru showed some spunk and granted political asylum to the Dali Lama. This antagonized the Chinese who declared Nehru as a "running dog of imperialism". The border with India sealed and trade with India stopped. In this entire episode, Nehru could do nothing, as much earlier he had frittered away India and Tibet's chances by his dubious policy of non-intervention in Tibet. In one stroke he made China the dominant power in Asia and this was reflected in the 1962 war, which resulted in the rout of the Indian army.
History records that Nehru frittered Indian and British interests in Tibet and forever lost Tibet as a buffer state. The clock cannot be put back and now the Indians have the Chinese on India's border. In this entire period, Nehru was bested by Mao who reduced Nehru's stature to a second rate leader in Asia.