This story is an excellent example of several things, including what can be done with a chronology. A chronology is a slice of real history that tells about events that happened during that period. But we like to make sense of our lives, and if we can, of history. It would be very difficult to make sense of the invasion and occupation of a peaceful nation by a conquering army. In the larger scheme, Tibet is probably a strategic military location from a defensive point of view - control the mountain passes and you prevent access by foreign invaders.
History is a bone-yard of conquered nations that makes very little sense.
Events mean very little unless you can show the human impact. Heinrich's odyssey showed us Tibet through the eyes of a foreign resident taken into the culture, but his real journey was that of personal transformation. This is the stuff stories are made of, and are rarely found in chronological events unless the writer digs really hard to put one together. There are two excellent examples of character transformation in the story. The first is a turning point at which the extremely self-centered Heinrich sees the consequences of his behavior and decides to be different.