Thus, China's President repeatedly sent letters and envoys to the Dalai Lama and to the Tibetan Government asking that Tibet "join" the Republic of China.
The letters are a formality, Tibet has no choice but to join China. 
( z1 formality :domain ( z2 letter ) :ARG0-of ( z3 cause :ARG1 ( z4 obligate :ARG1 ( z5 province :name ( z6 name :op "Tibet" ) ) :ARG2 ( z7 join :ARG0 z5 :ARG1 ( z8 country :name ( z9 name :op "China" ) ) ) ) ) )