read below about maurya and gupta
It is important to note that except for the Maurya period lasting barely a hundred years, and even then it was more because of diplomacy rather than conquest under none of the other dynasties did the Hindu governments ever rule over Pakistan. They always remained east of river Sutlej.
"At the close of Samudragupta’s triumphal career (4th century AD) his empire --- the greatest in India since the days of Asoka --- extended on the north to the base of the mountains, but did not include Kashmir…. Samudragupta did not attempt to carry his arms across the Sutlej or to dispute the authority of the Kushan Kings who continued to rule in and beyond the Indus basin." (Oxford History of India, By VA Smith).
"Harsha’s subjugation of upper India, excluding the punjab, but including Bihar and at least the greater part of Bengal, was completed in 612 AD." (Ibid)
"Politically during the time when Hellenism in the south Asian sub-continent was decaying and the centuries afterward, the north-west remained separate from northern and central India. The Gupta empire, which at its height in the middle of the 4th century AD, and the empire of Harsha in the middle of the 7th century AD barely reached into the Punjab and included none of Sind." (Pakistan and Western Asia, by Norman Brown)
"Throughout most of the recorded history the north-west (i.e. Pakistan) has normally been either independent or incorporated in an empire whose centre lay further in the west. The occasions when it has been governed from a centre further east (India) have been the exception rather than the rule; and the creation of Pakistan which has been described as a geographer’s nightmare is historically a reversion to normal as Pakistan is concerned." (A Study of History, by AJ Toynbee)
now put that in your pipe and smoke it