Martial Counterstrike

Your Strength or Dexterity increases by +1.

If a creature moves within 5 feet of you (melee range) and tries to attack you with a melee attack, you can make an attack of opportunity, using a melee attack, after their attack if it hits or misses. If the target misses you can as a free action move 15 feet without provoking an attack of opportunity from the countered target.

You can only make a martial counterstrike, if you haven't equipped medium or heavy armor nor shields.