Everything is, as they say, a matter of perspective. And of relation, of one to another, to others.
Hong Kong is a small place. As a city in its own right, its 7.3 million people make Hong Kong the 46th biggest city in the world by population, and the 104th biggest country in the world, bigger than 129 others.
In terms of land area too, Hong Kong is small, dwarfed by the other contested territories on China’s peripheries.
Tibet is enormous. Its total area, comprising the traditional three provinces of U-Tsang, Amdo and Kham, is 2.5 million square kilometres, making it the tenth biggest country in the world, just behind India, Argentina and Kazakhstan.
China invaded Tibet in 1950, and in 1965 established the Tibet Autonomous Region, a misnomer if there ever was one. It comprises 1.2 million square kilometres, less than half the size of traditional Tibet, and more Tibetans live outside the TAR than inside it.
Xinjiang, whose full name is Xinjiang Uighur Autonomous Region, another misnomer, or East Turkestan to those who don’t accept Chinese rule there, is also huge — 1.6 million square kilometres. (I prefer to avoid the term “Xinjiang” since it is inherently colonial, meaning in Chinese “new frontier”, clearly from the Chinese perspective. It is used here solely to designate the XUAR, the entity set up by the Communist Party in 1955.)
China would look a lot different without Tibet and Xinjiang, which together make up about 42% of the area under the rule of the Communist regime.[Source]