The Unknown Soldier, novel by Alan Robertshaw.
Spring 1971. As the snows melt on the Tibetan Plateau, the last desperate chapters of a secret and forgotten war unfold. After twenty years of fighting, a few Khampa rebels, with ever dwindling CIA support, are now the only resistance to the Chinese, occupiers of Tibet for twenty years. Eager for adventure, an ex-British soldier known only as Smith is drawn into this alien and fast disappearing world. In constant danger, he and a small band of rebels range across the harsh Tibetan landscape, harrying the Chinese wherever they can. But as a web of intrigue stretching from London to New Delhi, Kathmandu and Lhasa begins to engulf him, Smith comes to realise that the Chinese are not his only enemy. If he is to survive, he must escape from the Land of the Snows. And a young nun is determined to make the journey with him so that her culture will survive in the West.