In 1911 the Tibet Mongol relationship came to its final end with the fall of the Manchu dynasty. Tibet formally declared its independence in 1912 and continued to conduct itself as a fully sovereign nation until its invasion by China in 1949. Tibet governed itself without foreign influence, conducted its own foreign affairs, had its own army and operated its own postal system. Tibet enjoyed de facto recognition by its neighbors as well as by Britain, with whom Tibet entered into a series of treaties regarding travel and trade. Effect of the Chinese Invasion Tibet was an independent state at the time of the Chinese invasion and, under international law, states are presumed to remain in existence until that assumption can be rebutted.
China is unable to show that it has legally acquired title to Tibet since the forceful annexation.
The delegation was forced to sign the agreement under threats of violence and was denied an opportunity to consult Lhasa beforehand. Upon learning of the treaty , Lhasa immediately telegraphed Beijing to declare that the treaty was unacceptable. It is also important to note that Chinese troops were occupying large parts of Tibet at the time this treaty was signed. Since this treaty was signed under duress it was null and void since, according to Article 52 of the Vienna Conventions of the Law of Treaties, any agreement signed under duress is void. Furthermore, China began to violate the terms of the agreement immediately following its signing.