There are a few important tidbits that are of interest before trying to interpret any form of conflict between two particularly poorly documented cultures. The background is that no battles were technically ever recorded to our current knowledge. But the fact that Graeco-Roman sources often mentioned how Arsacid monarchs needed to go east in order to secure their frontiers, and the fact that some Parthians under the lead of Gondophares went further East into India, securing his position as far as the Mathura corridor according to archaeological evidence such as Indo-Parthian coinage and the enigmatic stone palettes, in the wake of the Indo-Scythian relegation into the Western Satraps and the emergence of the Kushans under Kujula Kadphises, and including the vast number of Parthian-style fortresses from the banks of the Oxus at Merv to the stretches of coastal Gedrosia in Bampûr and Panggûr as well as the intensive fortification works during the Sassanian era are strong indications towards the hugely importance and urgency of protecting the interests there.

Because armies were quite similar between the more settled Saka nobility in the Indus, as well as the Kushans in comparison to the Parthians, the battles must have been particularly gruesome and exhausting, just like the battles between the Diadochoi were prone to have turned into butchery. The situation turned particularly sour for the Parthians when they lost their prime middle-man position to the Kushans as far as the Silk Road was concerned; when the Kushans finally carved for themselves an empire stretching from the Oxus, Ganges and the Tarim, the Arsacid hegemony shrank considerably more than under any Roman influence. For one, they had now no direct access to their Chinese contacts but through the Kushans. It is hard to imagine that no conflict would have ensued as a result of conflicting interests.

This rationale must therefore have been a historic precursor to the later conflicts between the White Huns/Hûnâ and the Sassanians which fortunately are somewhat better documented. We are clearly able to recognize a pattern and therefore make a more reasonably sound assessment on the economical value of the area. This battle-ground was therefore quite easily compared to the conflicts of the Euphrates area. Let me enumerate a list of the principal powers of Central Asia and Bactria in rough terms from post-Alexandrian antiquity to before the advent of Islam:

* The Seleucid empire
* The Mauryan empire
* The Graeco-Bactrian kingdom
* The Indo-Greek kingdom
* The Kangju/Ta-Yuan/Soghdian kingdoms
* The Parthian empire
* The Indo-Scythian kingdom
* The Yuezhi/Tocharii
* The Indo-Parthian kingdom
* The Kushan empire
* The Sassanian empire
* The Indo-Sassanians
* The Chionites/Red Huns/Xîyûn
* The Hephtalites/White Huns/Hûnâ
* The Gök-Türkic confederal Khaganate
* The Indo-Hephtalites
* The Turk and Kâbul-Shâhî kingdoms

Persianates, Hellenistic powers, Indian influences, eventual nomadic incursions and finally the advent of the Turkic tribes. The list is a vast simplification of what actually happened, as power was ceded back and forth sporadically and erratically.

I hope this answered your question conclusively.