Initially, the term Uttarapatha referred to the northern high road, the main trade route that followed along the river Ganges, crossed the Indo-Gangetic watershed, ran through the Punjab to Taxila (Gandhara) and further to Zariaspa or Balkh (Bactria) in Central Asia.
According to Buddhist texts, Kamboja and Gandhara, two of the sixteen Mahajanapadas or great nations referred to in the Anguttara Nikaya and Chulla-Niddesa belonged to the Uttarapatha.
[1] The Buddhist texts include the remaining fourteen of the Mahajanapadas, namely Kasi, Kosala, Anga, Magadha, Vajji, Malla, Chedi, Vamsa (or Vatsa), Kuru, Panchala, Matsya (or Maccha), Surasena, Avanti and Assaka in the Majjhimadesa division.
Buddhist and Puranic sources attest that the merchants and horse-dealers from Uttarapatha would bring horses and other goods for sale down to eastern Indian places like Savatthi (Kosala), Benares (Kasi), Pataliputra (Magadha) and Pragjyotisha (Assam).
It refers to Uttarapatha (northern highway) which linked the territories of Kirata (perhaps of Magadha), Kamboja, Gandhara and Yavana countries (Shanti Parva, 207.43; Foreign Trade and Commerce in Ancient India, 2003, p 107, Prakash Chandra Prasad) Documentation exists that the nations from the Uttarapatha like Kamboja, Gandhara and Kashmira were actively engaged in commercial intercourse not only with the states of Gangetic valley but also with Brahmadesh, Suvarnabhumi, south-west China and other nations in the Southeast Asia [citation needed].
When the Chinese envoy Chiang Kien was in Gandhara (circa c 127 BCE), he found to his great surprise that bamboos and textiles from south-western China were sold in the local markets.
Some merchants from northern India had settled in Myanmar, in the ports and towns located at the mouths of Irrawaddy, Citranga (Sittang) and Salavana (Salween) rivers.
Dr Don Martino notes that the merchants from northwest Kamboja had been conducting horse trade with Sri Lanka following the west coast of India since remote antiquity (Epigraphia Zeylanka, Vol II, No 13, p 76).
A Pali text Sihalavatthu of the fourth century specifically attests to a group of people known as Kambojas living in Rohana in Sri Lanka.