Centurion: Defender of Rome is a turn-based strategy game where you play as a young Roman legionnaire in 275BC. Your goal is to conquer the known world through force or diplomacy, fighting on land and sea. You start with one province, Rome, and one legion, and must complete the game by conquering all provinces on the map.
The gameplay involves two main parts: micro-managing your provinces and military conquest. In your provinces, you set up tax rates and make people happy by organizing games, such as chariot races or gladiatorial combat, which start action mini-games where you control the participants. You also raise legions or strengthen them in any province you control, each with different strengths. You can move a legion to a neighboring province.
When entering a province you don't yet control, you speak with the ruler and try to convince him to give it to you for free, but this is unlikely, and you often have to fight. When your legion attacks or defends a province, the game switches to an isometric view of the battlefield, where you give orders to your legion and watch as they battle the enemy forces.
Finally, you can buy warships and engage in naval battles with the enemy fleet, represented as action mini-games depicting duels of flagships. The outcome of these battles depends on the strength of your fleet.