User blog comment:Master Sima Yi/Assassinews 25-03-'13 — Assassin's Creed IV: Black Flag gameplay trailer/@comment-4829046-20130516052015/@comment-4829046-20130516052713

Here's how you do it. You have to time it right though so I suggest you play a mission with infinitely spawning guards(for me it was the Silas assassination one) and when you see the red cursor, indicating a guard approaching you, simply press the attack instantly before he attacks and voila! he is counter-killed without needing to use any defensive moves. The move is tricky however and you only get a one second window and it fails when there are too many guards. The move highly reminisces the old counter in the previous games.