From the game description:
With Rally Round the King you can fight large fantasy battles by themselves or wrapped in an easy to use Campaign System. But what if you want to fight Roman Legions against Germanic invaders? Or Norman Knights versus Saxon Huscarls? What about a good historical set of rules? Look no further! Just drop the fantasy rules from Rally Round the King, add this supplement and you have a historical mass battles game. We’ve included over 145 historical armies from 3000 BC to 1500 AD, each with a Basic Army and using Recruiting Rolls to work with the Campaign System from Rally Round the King. No Dragons, Trolls, or Elves, just Egyptian Chariots, Roman Legionaries, and 100 Years War Longbow men.
Get the supplement HERE.