Of the four Amdo languages, the Rtahu language is used in the most southern part. Linguists have identified Rtahu as a variety of Amdo, but the Rtahu claim to culturally belong to the Khampa Tibetans. They have been officially counted as members of the Tibetan nationality in China - which numbered almost 4.6 million people in the 1990 census.
The Rtahu language seems to be transitional between Amdo and Khampa Tibetan; these two are reported to have about 70% lexical similarity. The Rtahu language contains two dialects: Braghgo and Tahu.
Padmasambhava, a Tibetan sage, gave the following prophecy in the eighth century: "When the iron bird flies and horses run on wheels, the Tibetan people will be scattered like ants across the world and the Dharma will come to the land of the Red Man." In October 1950 the Chinese army invaded Tibet from Sichuan. Another garrison moved southward from Xinjiang into western Tibet. Tenzin Gyatso, the 14th Dalai Lama - who himself is an Amdo Tibetan - fled into India. From his base in Dharamsala, northern India, the Dalai Lama has continued to lobby for the liberation of his people.
Between 1913 and 1950 Tibet tried to assert its authority as a separate nation, with its own flag, passports, and currency. Tibetan passports were only accepted as legal documents by Great Britain, India, and the United States. A Tibetan stamp was printed in India in 1910, bearing the image of the Dalai Lama. "These were rejected by the Tibetans. The Dalai Lama could not be placed on a stamp as it might get trodden underfoot, which would bring dishonor to him. Besides, who was going to strike his head with a great metal franking hammer?"
All Rtahu Amdo Tibetans are fervent Tibetan Buddhists. No more than a handful have ever heard of the existence of Jesus Christ.
In the past, some mission agencies considered working among the Tibetans but found excuses easier than the hardships the workers would have had to endure. In 1922, Dr. A. Reeve Heber of the Moravian Mission in Ladakh was challenged to expand his work into Tibet. He responded, "When once the country has been opened to the missionaries, I do not think that we are in a very good position to enter it from any of our present stations. It is almost entirely inhabited by nomads among whom it would be very difficult to work."