In Field of Glory II, Custom Battles allow players to build their favourite battle with a wide range of options at their disposal. You can choose between 78 army lists of the period (check here for the entire list!), you can set the force size, the map type, and many other settings. An interesting thing when you select your enemy is that you can restrict the selection to geographical and historical consistency (or you can just go ahead and make the Ancient British fight against the Sarmatians!).
I picked up the Roman Army (219 – 200 BC) and, for my opponent, I decided to face the Macedonians (260-148 BC).