I don't get where this whole "No one's ever conquered Afghanistan" thing comes from. In addition to Persians and lunatic Greeks who decided to live there the area known as Afghanistan has been held by a variety of different kingdom from the Mauryans, Gupta, Tibet had Kabul apparently at one point before the Umayyad showed, then you have the Ghaznavids and Ghorids (maybe you consider them Afghan?) Delhi Sultanate, Mughals, Safavids and so such. For some of these states Afghanistan was an integral part of their empires.