When the user engages in battle, neither the user nor the enemy can double attack. Learned by Generals at level 5.
Wary Fighter is an extremely useful skill for tanking, as it prevents the nimblest foes like Swordmasters and Master Ninjas, who often lack much strength to deal with high defense units like the General. Since most units are capable of doubling slow units, this skill will prevent them from doing so. When combined with a unit with high physical and magical defense, they can become a near-impenetrable wall where it will be very difficult to overpower them.
However, Wary Fighter can also harm the user if their speed is high enough, since they cannot double back. The user (who tanks with this skill) must also have sufficient defensive stats, as skills like Lethality will render the skill's effects void.
Note: Despite the skill description, Brave weapons (including Lightning, Snake Spirit and the Crescent Bow) can still perform follow up attacks. It simply prevents the brave weapon user from attacking 4 times in a row.