This Silk Road connected the Roman Empire to India and China for a while. I recall one commentator about these caves and crumbled monastic ruins in the desolate desert of the Tarim Basin, who mocked the monks who went to such efforts to create long-lasting religious establishments that were overcome by time and hostile religions. As if the Buddhists who created these works of art were not aware of the law of transience which is one of the central doctrines of their creed! What a jerk. What these works of art did help accomplish was the transfer of Buddhist iconography and doctrine from one great civilization (India) where it was doomed to Hindu and Muslim extermination, to another (China, and hence Korea and Japan), where it survives to this day.
Maybe someday a few hundred or thousand years hence a religious scholar will unearth these statues and have to rewrite the history of American religious art to explain their significance. First one is Vajrasattva, then Yeshe Tsogyal, White Chenrezig and last White Tara.