A portion of a Ubisoft forum Q&A with Ubisoft's Jason Vandenberghe, Creative Director. This portion of the Q&A is all about blocking...

We believe that the ability to block bullets with your sword is the sacred, God-given, inherent right of every katana-wielding cowboy samurai badass. To that end, you simply hold the (A) button to block – swords or bullets, same/same. Now, this won’t grant you 100% protection against (say) a machine gun or burst-fire – but it does help, for sure. Further, there’s a feature in our counter system that lets you send bullets back at the shooter – if you manage an “active” block (we’ll probably talk about this later) with the right timing, you can kill ‘em with their own bullets. Which, you know, saves ammo and stuff. Oh, and it kills them, too.