In my spare time I’ve been working on a card game called Bastion where two players duke it out in a battle reminiscent of warfar in the 16th through 19th centuries. During this time period they had big solid fortresses, and an incredible variety of techniques for capturing those fortresses.
Here is a topic I started on GoodGamery to discuss the development of Bastion.
The core of the game has one player buying defenses while the other player tries to breach them. Most of the cards they use will be similar, except that the defender has access to a bunch of fortifications, while the attacker will use specialized units like miners, sappers, siege ladders, and so on.
Each of the units has a couple corresponding Combat cards, which represent maneuvers or tactics that the player’s troops use in battle. The more expensive units have access to more flexible or more powerful Combat cards, and specialized troops have specialized Combats. By moving all of the specialized rules for the units onto their combat cards, it keeps the units from having a bunch of special keywords, numbers, and abilities. Instead, they have only a cost and a health, and the rest gets to be artwork. All of the complicated stuff is on the combat cards, and since you only pick from a couple of those per turn, the combat plays out pretty simply.