The Indo-Parthian kingdom was based on the power of the Sacaraucae, also known as Scythians, who were distant relatives of the Parthians, who had been forced south-westwards by the Yueh Chi into Parthian lands during the mid to late 2nd century BC. The wars against the Saka were responsible for the death of Phraates II, and occupied much of the reign of Artabanos I, who was finally able to exert a measure of control over the western Saka in the region of Merv, Margiane, and Aria as witnessed by Parthian coins struck there. It was not until the reign of Orodes I that Parthian control was fully restored over these regions. The Sacaraucae were able to retain a measure of independence and began striking their own coinage as early as 80 BC. The Indo-Parthian kingdom was founded by the first of several kings named Gondophares in the late first century BC. Gondophares, as well as being a Saka king, was probably a member of the Suren family, one of the seven major noble houses of the Parthians, whose feifdom was in Seistan, by now known as Sakastan, on the eastern borders of the Parthian empire. Indo-Parthia expanded to the east, sometimes as vassals of the Parthians and sometimes independently, eventually stretching to Pakistan and northern India. Indo-Parthia suffered major defeats at the hands of the Kushans in the late first century AD, and eventually was reduced to the area of Sakastan and Arachosia until their conquest by the Sassanians during the 3rd century AD.