As regards the situation in Τibet, I’ve said elsewhere that history is a slippery ally when forced into the service of contemporary political disputes.
Let’s set aside the Mongols for a moment. They ruled an empire that stretched from Korea to Kiev, so one could use the Khans to make all kinds of territorial claims. Yuan (1279-1368) rule was extremely short in duration anyway, and most of the territories outside China proper were beyond Ming (1368-1644) control for nearly 300 years.
The Qing Dynasty (1644-1912) is a good place to start as the Manchus did maintain garrisons on the Τibetan plateau while administering the region through local elites. The Qing rulers, great patrons of Lamamism, consolidated their rule by maintaining cultural and religious ties with Τibet beyond mere military occupation. They also–generally but not always–ruled with a light touch, allowing relative autonomy in religious and cultural matters, which suited the situation quite well. The Qing Dynasty was, after all, a large, multi-ethnic empire, and maintaining order and peace in outlying territories was the utmost concern.
The problem is that the PRC is a nation-state, and the demands a nation-state places on its people are different than those of an empire. It is not enough that Tibetans merely pay taxes and not revolt, they must also identify with the nation-state first and foremost, with other cultural and religious aspects secondary to the demands of modern state building. Empires want to be respected, nation-states want to be loved. That’s a sticky wicket the Qing never had to face.
It’s not surprising that when we look at the world’s hot spots we see the legacies of colonialism and decolonization. As empires give way to new forms of political organization there is resistance and tension. Modern states attempt to preserve the territories bequeathed to them from empires of old, while subject peoples seek greater autonomy and even independence.
Unfortunately, history is a poor arbiter of who gets what, and too often (as in the case of Τibet) history becomes warped and carved, tugged and torn, by states and separatists, to suit the political demands of a contemporary crisis.
My own views on the situation are consistent with my views on China in general: I believe the citizens of Τibet, as with those in the rest of China and the world, should be free to speak and write and criticize without fear of censorship or government suppression, and to demonstrate peaceably if necessary. They should be able to worship and participate in cultural practices as they see fit, to be educated in the language of their choice, and to be able to pursue these rights in free, unbiased, and independent courts. When those are accomplished, whether Tibet remains a part of the PRC, becomes an independent state, or ends up something or somewhere in between, is a matter for the Tibetan people and the PRC government to then resolve peacefully through dialogue and negotiation.