The Kushan were a branch of the Yuezhi confederation. Previously a nomadic people residing in eastern Central Asia, the Yuezhi moved southwest and settled in ancient Bactria. They had diplomatic contacts with the Roman Empire, Sassanid Persia and Han China. While much philosophy, art, and science was created within its borders, the only textual record we have of the empire's history today comes from inscriptions and accounts in other languages, particularly Chinese. The empire declined from the 3rd century and fell to the Sassanid and Gupta Empires.