Combat in War Haven is dominated by spatial tactics. It doesn't matter how deadly the cards in your hand are if you can't get them to the target. Likewise, cleverly avoiding an attack can often be the best defense.
Defensive play is especially key with your commander character, after all, if he dies you lose the game. You almost never want your commander to be on the front lines, but in the rare cases you do need put him on the offensive it's best to make sure you have every possible card available. For this reason, it is important to be able to stall when you see an enemy approaching your commander.
One of the best stalling actions available in the game is the "rook," a basic blocking maneuver. The first move here is to get into position. Move your commander, or other vulnerable character, up behind your intended defender. Now you're set, and if an enemy approaches your "defendee" from either side, you simply move them to the opposite side and drop your defending character in between you. Because this only takes two actions, you can use the third to attack with your defender if the enemy is in range, or just attack before moving. A fun spell to pair up with this technique is the radium mortar, since the approaching enemy is likely to have to attack several times to get anywhere.