An interesting paragraph on Tibet

I don't know the history at all... but here is an interesting paragraph from a book I am busy reading called `Power' by Bertrand Russel:

When a British military expedition invaded Tibet in 1905, the Tibetans at first advanced boldly, because the Lamas had given them magic charms against bullets. When they nevertheless had casualties, the Lamas observed that the the bullets were nickel-pointed, and explained that their charms were only effective against lead. After this, the Tibetan armies showed less valour.

So:

1. If Tibetans aren't opposed to fighting in defense, why aren't they fighting now?
2. Why did Britain invade Tibet? Does it have some sort of mineral value?
3. I have heard stories of the great fight for a `united China' and the tremendous prosperity this brought relative to years of warring. The US also had its own war when the South tried to break away from the North. Is this part of China's motivation?
4. Land has throughout History being taken by force. From Indians by the US, From Aboroginies by Australians, From non-Zulus by Zulus, From Afrikaners by the English, From Native English by the Normans... Presumably all land where ownership is claimed was either taken by force from someone else or defended by force from others who also desired it. Do Tibetans have a stronger claim to Tibet than anyone else?

I am not trying to justify what China is doing, I am just trying to understand why they are doing it...