It has existed ever since, why the hell they will otherwise claim Tibet.This middle Kingdom phenomenon is a recent creation.
India - China war followed China's annexation of Tibet, which Mao and gang thought to be China's historical right (see the pattern right from 1950s?). Nehru being the cuckold he was, actually assisted by looking the other way. Hindi Cheeni Bye Bye bullshit galore. I will avoid retelling the entire story as you may very well know it.Mao had not thought about it at that time. At that time it was simply teach Imperialist India a lesson and show the Chinese awaam that they are the good guys and the coward Indians are thieves.
It was only when India started to appear as a possible threat to Tibet -- again Nehru's weird schizophrenic policy giving Dariyai Lamma refuge -- and Aksai Chin being the path to Tibet from Xianjiong that this war started brewing.
In short, it was always "China's historical rights" mindset of China coupled with fear of losing Tibet.
Had Nehru not been the cuck he was, Tibet could very well have been a protectorate of India and we would be having some Tibetian in this forum and may be in our college campuses as well.