OPPIDUM: Celtic Warriors Against Roman Legionaries

From BoardGameGeek:

OPPIDUM is a Tactical level skirmish board wargame that takes place during the 50s BC, when Julius Caesar successively attacked the various Celtic and Germanic peoples in Western Europe and (future Great) Britain. The game uses the concepts and scale of the Cry Havoc series. The different scenarios will allow you to simulate ambushes, attempts by the defenders of Alesia to break the siege or the landing of Roman legionnaires on a Britannia beach defended by warriors on chariots. -description from the publisher