and . The Indo-Iranians and their expansion are strongly associated with the Proto-Indo-European invention of the chariot. It is assumed that this expansion spread from the Proto-Indo-European homeland north of the Caspian sea south to the Caucasus, Central Asia, the Iranian plateau, and the Indian subcontinent. The Mitanni of Anatolia The Mitanni, a people known in eastern Anatolia from about 1500 BC, were of possibly of mixed origins: a Hurrian-speaking majority was supposedly dominated by a non-Anatolian, Indo-Aryan elite. There is linguistic evidence for such a superstrate, in the form of: a horse training manual written by a Mitanni man named Kikkuli, which was used by the Hittites, an Indo-European Anatolian people; the names of Mitanni rulers and; the names of gods invoked by these rulers in treaties. In particular, Kikkuli's text includes words such as aika "one" (i.e. a cognate of the Indo-Aryan eka), tera "three" (tri), panza "five" (pancha), satta "seven", (sapta), na "nine" (nava), and vartana "turn around", in the context of a horse race (Indo-Aryan vartana). In a treaty between the Hittites and the Mitanni, the Ashvin deities Mitra, Varuna, Indra, and Nasatya are invoked. These loanwords tend to connect the Mitanni superstrate to Indo-Aryan rather than Iranian languages – i.e. the early Iranian word for "one" was aiva. Indian subcontinent – Vedic culture The standard model for the entry of the Indo-European languages into the Indian subcontinent is that this first wave went over the Hindu Kush, either into the headwaters of the Indus and later the Ganges. The earliest stratum of Vedic Sanskrit, preserved only in the Rigveda, is assigned to roughly 1500 BC. From the Indus, the Indo-Aryan languages spread from c. 1500 BC to c. 500 BC, over the northern and central parts of the subcontinent, sparing the extreme south. The Indo-Aryans in these areas established several powerful kingdoms and principalities in the region, from south eastern Afghanistan to the doorstep of Bengal. The most powerful of these kingdoms were the post-Rigvedic Kuru (in Kurukshetra and the Delhi area) and their allies the Pañcālas further east, as well as Gandhara and later on, about the time of the Buddha, the kingdom of Kosala and the quickly expanding realm of Magadha. The latter lasted until the 4th century BC, when it was conquered by Chandragupta Maurya and formed the center of the Mauryan empire. In eastern Afghanistan and some western regions of Pakistan,