How many Spartans died in Halo 4 and Halo 4 Spartan OP’s do we know? And does anyone think their should be a spin off game on the Spartan 4’s kind of like Reach to show something dramatic with their numbers?
Confirmed deaths include:
Castle Team
Mountain Squad
The leader of Fireteam Switchback
As a strong advocate of the Spartan-IVs, I would love a game focusing on them. It’d at least give us more info on them, which we (I) definitely need.
There’s also a few more recent casualties from Escalation. 
Fireteam Redshirt reporting for duty!
But yeah, besides Castle and Mountain an individuals, nailing an exact number is difficult.
> Fireteam Redshirt reporting for duty!
AKA Crimson on Legendary w/ skulls.