From Persia, the Aryans arrived in what is now Pakistan around 1400 B.C., although scholars tend not to associate them with the decline of the Indus Valley civilization. Little archeological evidence of their presence remains, although their written scripts are important sources for the origin of the Indian caste system and Hindu religious beliefs.
Alexander the Great crossed the Hindu -Kush in 327 B.C. but his battleweary troops were not inclined to travel further east, so he sailed down to the Indus delta and from there returned to Babylon, where he died in 323 B.C.
In the centuries that followed, many peoples from different parts of Asia occupied what is now Pakistan: the Indians from the Mauryan empire, the Greeks of Bactria, the Huns, the Arab Moslems in A.D. 711, and then the Turks, followed much later by the mighty Moghuls.