Ptolemy while identifying the course of the river Indus gradually unfolds one region after the other through which this river or its tributaries passes. As the places mentioned relating to its course find them positioned at upstream regions, identification of one place unfolds the relative position of the other.

The Periplus mentions Arachosia(or Arakosia) as a tribe along with Aratii, Gandaraei, and the people of Poclais who were then living in countries inland to Barygaza port. The Periplus also informs that Bucephalus Alexandria is a part of this region. And above this Arachosia is the war like nation of the Baktrians. From this explanation of the geography of the region around Arachosia near which is Bucephalus, it is clear that this river presents a wheeling picture of the Indus river course that passes through various places which are founded on hill-like positions on the bank of the rivers.

According to the epic Mahabharata, Aratta is watered by five rivers, and it was famous for its fine breed of horses. It is also called Arashtra in Sanskrit. While Gandaridaei or Gandariae people are identified with Gundi-vana of the epic, Kausiki identifies river Kusi which is a branch river of the Drusadvati of the epic flowing through the Kuru region. Padma purana mentions meeting place of this river with the Ganges at Kausiki.

A close look at the name Kusi reveals that there two different places in this name; one Kusi which identifies ancient Kasi, and the other Kusinagar that identifies the place of Mahanirvana of the Buddha. The former is at the foot of Mt Meru near which was the settlements of the Baktrian people.

We find after the death of Alexander when his dominions were distributed among his generals, this region of Arachosia came under Seleucus. When he was defeated in his war against Chandragupta Maurya, Paropanisus was made the boundary between the new empire of Seleucus, This happened through a treaty  in 303 B.C. by which  Alexander’s successor Selecus gave the provinces of the Paropanisus, Aria, Arachosia, and Gedrosia to the emperor of Magadha. We find that Asoka inherited these provinces from his grandfather Chandragupta.

McCrindle says, ‘Arachosia extended westward beyond the meridian of Kandahar, and was skirted on the east by the river Indus. On the north it stretched to the western section of the Hind Kush and on the south to Gedrosia…..’ . This geographical identification for the Arachosis shifted it from its ancient position and founded it beyond the borders of the present political India. This statement does not take into account the neighbourly position of Aratii, Poclais, and Gedrosia which were identified with Paropanisus range of mountains.

Ptolemy makes a list of names of places in the Arachosia which includes Arakhotos Krene, Phoklis, Arikaka, Alexandreia, Rhizana, Arhaka, Sigara,  Khoaspa, Arakhotos, Asiake, Asiake, Gammake, Maliane, Ozola or Axola and  Dammana. An no attempt has been made by scholars who put the entire Arachosia region out of India.

Arachosia as the name suggests and as it identifies itself with the ancient Kasi of the Kosala kingdom, same as Caesarea of the history of Rome, and as it is neighbourly to the Baktrians at the foot of Mt Meru, it poses no difficulty in finding its geographical situation on the bank of the river Indus that opened a passage for Alexander and his soldiers to enter India through it.