How do you kill Sassanid Immortal Cavalry?

[Braden]

Oh, lots of options. Ok, before you even attack them - target the unit with assassins en-mass. On the battlefield - Swamp them with Lanciarii (initially on Guard, then turn that off) AND/OR, use Plumbatarii behind a line of Lanciarii to pelt them with their iron "darts" OR take a General on a trip down South East in the desert and see if you can get some Merc Elephants.

OR just besiege them until they have to come out. In the open field they are less effective as you can encircle them and stop them doing damage (or lead them away with skirmish cavalry).

[Cras]

I think the best way to prevent fight the sassanids is to become them..

I actually just did that in a new campaign :-)