I suspect it was typical of the forces that attacked
Minas Tirith: a lot of Eastern
men and a lot of
orcs.
I was intrigued by the cavalry, as I did not think orcs rode
horses.
The concept of
Easterling cavalry had me scratching my head.
Southrons would seem to make more sense, as they the would not need to go all the way to the
Black Gate to join up with
Sauron's forces.
But then I realized I was thinking of the
Easterlings taking the same road from the Black Gate to
Minas Morgul as
Gollum,
Frodo and
Sam did. Might cause a jumble (at least) at narrow passages (like the place
Faramir's
rangers attacked the Southrons) if south-moving Easterlings "collided" with north-moving Southrons at such a place.
Small fact which had temporarily slipped my memory:
Mordor was surrounded by
mountains in the north, west and south - but was open to
the east! So Easterlings could have headed towards the passes to Minas Morgul by a much more direct route than the big detour north of the mountains to the Black Gate, then south to Minas Morgul. And while cavalry certainly couldn't navigate the stairs to
Shelob's Lair, it could quite well have been possible along the lower pass road that Gollum, Frodo and Sam had to avoid. And then
Khamûl was an Easterling, might have done the "recruiting".