Analysis of information sources in references of the Wikipedia article "Seleucid–Mauryan war" in English language version.
Chandragupta soon conquered the whole of the Punjab. Some of the land in the extreme north was held by the Greek general Seleucus Nicator. Chandragupta fought a long campaign against him and finally defeated him in 303 B.C. He acquired the territory across the Indus in part of what is now modern Afghanistan. There was also a marriage alliance between the two families. In addition Chandragupta had conquered parts of Central India, so that by the time his reign ended northern India was under the Mauryas.
Certain areas in the north-west were acquired through the treaty with Seleucus... It has been suggested that the territory ceded consisted of Gedrosia, Arachosia, Aria, and the Paropamisadae.
{{cite book}}: CS1 maint: date and year (link)