First and foremost, a card-driven wargame is not a cardgame. It is a wargame that uses cards. It still has a board and unit counters representing forces at the disposal of players. The central mechanics such as movement, combat and even victory conditions are also similar to conventional wargames. Central mechanics can be hex-and-counter wargames (Empire of the Sun), point-to-point wargames (Hannibal: Rome vs Carthage) or even Block wargames (Hammer of the Scotts). They can even be multi-player(Sword of Rome). For more on a basic wargame, please refer to the classic system.
At the start of each turn, players draw a number of cards as their hand. Each card can be used as an "event card" or an "operations" card. To make their moves, players have to play a suitable card from their hand.
In the first game of this series, a card is either an event card or an operations card. It was found that this arrangement is flawed in that a bad draw leaves a player without the ability to conduct any military operations. This makes for a bad wargame. In subsequent games using this system, players have the choice to use each card either for events or operations.
When used as an event, a card represent historic events, and are included to add chrome to the game. Each event affects the game by allowing players to make one specific action (adding reinforcements, change alignment/loyalty of cities, enhanced attacks, etc).
Operation cards enable a player to conduct military operations, usually represented by movement of forces under the direction of a leader. Leaders are graded by initiative, and good leaders can be activated by any cards, while those will lower initiative may be activated only by powerful cards. This handicaps the player, as a powerful card generally has a more power event associated with it. A special type of operation card, called campaign cards, allows a player to move more than one leader in concert, before the opponent can react. This represents the marshalling of resources to launch a board-based offensive. These campaign cards are rare, and are jealously hoarded for game winning moves.