This era of massive migration Motion and settlement Statement was particularly encouraged Influence by President Thomas Jefferson following the Louisiana Purchase , giving rise to Cause_change_of_position_on_a_scale the expansionist philosophy known as `` manifest destiny '' .

The conflict Hostile_encounter led to Causation a recorded Recording 20.77 million population reduction Cause_change_of_position_on_a_scale in Shaanxi and Gansu occurred Presence due Causation to migration and war-related death Death .

Many of the Tang generals and soldiers stationed Placing in the region were ethnically Turkic , and the prevalence of Indo-European languages in Central Asia declined Cause_change_of_position_on_a_scale with acceleration Cause_change_of_position_on_a_scale of Turkic migration .

This migration is regarded as one of the largest peaceful migrations in the world 's history .