evidence: It is isolated not only geographically, but also diplomatically. China enforced a long-held claim to Tibet in 1950, and it was subsequently incorporated into Chinese territory. [...] But in 1907 Britain and Russia agreed that both parties would deal with Tibet only through China, and China enforced what it saw as its claim on Tibet through a military invasion in 1910. [...] China believes Tibet to be an important reservoir of natural resources. It is the prime source of Asia's major rivers, and harbours extensive forest and minerals.