This is probably the first recorded full contact between Chinese and Caucasoids (Tocharians). During 200 BCs, China was again unified under the Han Dynasty. Kingdoms of the feudal period were vanquished and now Chinese military expansion were into realms of the non-Chinese. To Korea, Vietnam, the Huns and westward into lands of Caucasoid races (ie Tocharians and Sogdians)
People have this image of the Chinese being passive and non-martial. But, the first recorded history was that Chinese invaded and ruled over Caucasoid peoples (and not the other way around). This repeated again during the Tang Dynasty couple hundred years later.
We all know that Turkic/Mongol (Altaic) are regarded as the only well known non-European groups to successfully invade and subdue Aryan (Caucasoid) nations in the past. I would say the only group after them would have been the Chinese.