The Dahae had originally lived between the Jaxartes in the 4th-century BC, but gradually moved southward, possibly in the early 3rd-century BC. They first migrated southeast to Bactria, but were driven away, and as a result changed their course to the west. They gradually started settling in Parthia, a region in the south-eastern part of the Caspian Sea, that almost corresponded to present-day Khorasan Province of Iran and southern Turkmenistan. The region was then under the rule of the Seleucids. By 282/1 BC, Parthia was under considerable Parni influence. The Parni were not the only to migrate to Parthia, as the region was constantly receiving new waves of Iranian migrants from the north.