How do you perform a counter punch while playing Assassins creed brotherhood on xbox live?

To perform a counter punch in Assassin's Creed Brotherhood while playing on Xbox Live, you need to wait for an enemy to attack you. When they do, press the "B" button to Dodge or counter their strike. Timing is crucial; you must execute the counter just as the attack is about to hit you for it to be successful. If done correctly, your character will retaliate with a counter move.