use the term invasion is if the place is outside the borders of your country.
The land of the Uyghurs which is called Xinjiang literally means “New Frontier.” Even through language, it’s obvious this land does not “fit” with the rest of China but it does not stop the Chinese government considering it their own land. (FYI the Uyghurs are a Turkic people while most of China speaks Sino-Tibetan Languages).