How to Make Guards Willingly Fight One Another

I'm not talking about when an enemy might accidentally swing his sword at another trying to hit you, but actually going after other enemies. Here's how.

There are different factions of enemies in the game: Saracens (Damascus and Jerusalem), Crusaders (Acre), Assassins (Masyaf), and these other subfaction enemies, mostly targets and other mission based guards.

You can pit one enemy faction against another if one faction sees the other attacking Altair without actually seeing Altair (or else he will join in the fight against you). To do this, make sure an object is blocking Altair from the unaware enemy's line of sight. This won't work if the enemy fighting you is from a subfaction for some reason.

To give you a better idea, here are some videos. If you're wondering why I use the link to an embedded video in a forum instead of the original Youtube links, it's because I wouldn't have found this trick out if it weren't for the motivation of these my fellow AC fans.

The basic "how to".
http://thehiddenblade.com/altair-confessor-proof-enemy-factions-and-fighting-each-other

Also used to assassinate a target without ever hitting him.
http://thehiddenblade.com/templar-vs-templar-guard-assisted-assassination-tamir

Enlisting the help of a high level enemy to clear the area of guards (and a nice kill compilation starting at 8:10).
http://thehiddenblade.com/garniers-help-clearing-hospitalier-fortress