Swat River.

All this new geography is coming painfully. The Swat River valley is
in the northwestern corner of Pakistan. Of the archaeological horizon
associated with it (Swat Valley or Gandhara Grave culture), Mallory
writes in EIEC ("Swat Culture", p. 560):

--start quote--
The presence of the horse and the mode of burial have been connected
to the Bishkent and Vaksh cultures of Central Asia .... [T]he Swat
culture has been recognized to be in the right place at the right time
and bearing the right sort of culture to be identified with the
movement of Indo-Aryans, or given their specific location, possibly
Dardic or Nuristani-speaking people to the northwest corner of the
Indian subcontinent.
--end quote--

The pass in question here seems to be what my National Geographic
Atlas call Shandur Pass, leading into Gilgit River valley (this is in
the Pakistani-controlled portion of Kashmir). EIEC locates Bishkent
"in southern Tadzhikstan" ("Bishkent", p. 68); the map puts it way up
Amu Darya. Beyond this, I have no idea exactly where it is, and a more
westerly approach (via or west of the Afgan 'panhandle') seems more
logical, but my knowledge fails here.

The media has been giving us lots of stuff about this part of the
world. The pattern for the past several thousand years seems to be
mountain-dwelling warriors always ready to sweep down from Afganistan
into the Indus valley and points east. What you read of the British
Raj was their need to create and maintain a border, in order to keep
such raiders out.

Another thing you notice on current television. With lots of these
Afgans, if you gave them a shave and a haircut, and put them in jeans
and T-shirts, they would look perfectly in place on any European or
North American street.

I wonder just how long it's been since Iranian displaced Indic in this
part of the world.