the westward expansion of the tang dynasty began with their wars against the eastern turks, eastern tujue in chinese. taking advantage of the political discord in the eastern turkic khaganate, taizong annexed the territory of the eastern turks in 629, beginning a period of rule that would last for the next fifty years. the nomads were driven out of the ordos region and southern mongolia and taizong was declared a great khan by the defeated tribes, who surrendered and submitted to tang rule.