Also, before the 19th-century, the idea that "under Heaven, there is no land that is not the emperor's," was still prevalent in China. The idea of national territory as embodied in modern international law is something that only came about as a result of imperialism "knocking at the gate" in China.
天朝中國只要來朝歸順，什麼不可給？十九世紀以前的中國還有著「普天之下，莫非王土」的觀念，國際法上的領土觀念，還是被西方帝國主義「叩關」出來的。