In the late 5th century AD the Hephthalites, based in Tokharistan (Bactria), expanded eastward through the Pamir Mountains, which are comparatively easy to cross, as did the Kushans before them, due to the presence of convenient plateaus between high peaks. They occupied the western Tarim Basin (Kashgar and Khotan), taking control of the area from the Ruanruans, who had been collecting heavy tribute from the oasis cities, but were now weakening under the assaults of the Chinese Wei Dynasty. In 479 they took the east end of the Tarim Basin, around the region of Turfan. In 497–509, they pushed north of Turfan to the Urumchi region. In the early years of the 6th century, they were sending embassies from their dominions in the Tarim Basin to the Wei Dynasty. The Hephthalites continued to occupy the Tarim Basin until the end of their Empire, circa 560 AD.</ref>