to size it up

[Omanes Alexandrapolites]

It means that am unlimited number of mighty units, both your units, and the AI's, are permitted to be on the battlefield at any one time - this means that any re-enforcements that would normally break the limit will be allowed onto the field. However you can, sadly, only control twenty units at once and any-more have to be under the command of the AI, although they are on your side, or be given to you one-by-one as your units rout or get destroyed - that option is settable on the pre-battle screen.