Last night I fought a battle with my Macedonian army before the gates of Rome. I was sieging the city and the army got attacked by the traditional relief force. This relief force (a small Julii army of two, not full, legionnary cohorts and some velites) was relatively easily beaten.
The senatorial army was announced as a reinforcement army. Unfortunately they didn't make it to the battle, so I just had to get rid of the Julii.
When the battle was over, I noticed that Rome was empty! The Senate's army had just evaporated (a pity because there were a few good units in it like Praetorians, Praetorian cavalry, Urban cohorts and some siege artillery).
I couldn't assault the city, but when I broke off the siege, I could move in my army without any problem.
Isn't it a bit strange that an army that doesn't arrive on the battlefield in time, just disappears? Okay, they had the "no retreat possible" icon, but they didn't even arrive in time to make it to the battle so this shouldn't have counted, right?

Here are some pictures:




PS. Don't comment on the game year. I know I am a slow player