I think the card system is extraneous.

Another way for the gameplay:

The cards includes all orders excluding the basic orders to move troops and to attack. In each turn, each player would draw 1 card. They could keep the card if they decide not to use it. On their hand, they could have at most 3 cards. If a player has 3 cards, he must reshuffle one of them in order to draw a new one.

The cards are building orders, special movement, special attacks, and events.
Some special attacks requires the player to have two or three of the cards for that attack in their hand. For example, if the player picked a "fire tactics" card, it could be used during an attack to add additional damage. If the player had the "fire tactics" card plu a "dry weather" card, the damage of the fire tactics would times 4. If the player had both of those cards plus "westward wind" card, then the player can use the fire tactic card to attack units deeper westward, and it would damage units on multiple cells.

Once the player used those cards, they are reshuffled.


Other card ideas:

Nuclear Warhead Card: Allows the player to destroy all units in a square once. Requires a built nuclear silo.

Nuclear Silo Blueprint Card: Allows the player to build one nuclear silo. It takes three turns to build. This card can be seized if the building location is conquered while it is being built.

So suppose it is your first turn, and you drew a Nuclear Silo Blueprint Card. You could decide to keep it for later use, or to build it right away. If you build it, then once it is built, the card would get reshuffled, and your enemy could draw that card a build one. If you decide to keep the card and not build, then no one could use nuclear weapon.

Suppose it is your first turn and you drew the Nuclear Warhead Card. Again, you could decide whether to keep it or to reshuffle it when you have 3 cards. Suppose you want to get a nuclear silo built, so you wait for the Silo card. You waited for many turns but you didn't draw it. Then you suspect that your opponent is keeping the Silo. You could decide whether to reshuffle the Warhead so that you could get a better card, of you could decide to hold on to the Warhead card because you think that the opponent would definitely build a silo and use a nuke if he has both cards.


Landmines Card:

When you drew this card, it allows you to place landmines on a cell. Once they are placed, they could be triggered by either side when the current cell does not have any occupant of your side. Placing landmines is instant. Once they are placed, the card reshuffles. Your opponent can tell that you drew a card and you immediately used one card, but he cannot tell what you did.


Beer Card:

Increase the attack recharge of infantry at the selected cell for the current round. When you get this card, you don't need to use if right away, you can wait till you have a sufficiently large infantry-based attack before you open the kegs.