Altair the Confessor - Proof of Enemy Factions and Fighting Each Other
[Front-paged. -stabguy]
Here's a head turner: Guards in AC1 are capable of engaging in combat with one another. In this video are details of how it was meant to work.
Factions
There are three main factions of guards: Saracens, Crusaders, and Assassins. This is indicated by how one reacts when Altair is killed by one of the others. Get killed by a guard in one faction in front of a guard from a different faction, and he will start attacking him.
There are also other guards within a faction that will attack other guards in that faction. These seem to be mission-based guards wearing different clothing than the rest, like the guards outside of Talal's warehouse. However, the regular guards don't seem to attack them.
Combat Between Guards in the Game
Normally there are only two examples of guards fighting each other in the game. The first is the two assassins in the fighting ring. After ending practice, listen closely and you will hear them shout out the combat starting phrases, which proves they are using the regular fight scripting. Next is the battle of Masyaf in memory block one. You see Assassins and Crusaders fighting one on one. Besides the appearance of basic fighting with no combos, counters or grabs, they appear to have unlimited health until you get close enough. But it's scripted so that the assassin always dies in the fight.
How to Make Guards Fight Each Other
Now for the major highlight. After a long time searching, a way has been found to coax the enemies' bloodlust against themselves without Altair having to die. What you need to do is find a place where two different enemy factions are. Get in a fight with one and find a place where a wall conceals Altair, while the other is in plain view. If an enemy from another faction sees the other do damage to Altair without detecting Altair, they will attack that enemy.
In the video I demonstrate this with a Templar at the assassination location of Talal in memory block three. This just happens to be the place where I first found out the combat starting trick and has nothing to do with making it work.
To make the combat fair, I get the Templar to kill a guard by another who hadn't spotted Altair. So they both engaged each other, and... whoa, is that a combo kill animation? Since Templars are high level they can perform combos and counters. But why don't they do kill animations on Altair then? To make it simple, think of assassination targets. So you're supposed to kill them with the hidden blade, combos and counters with the sword or shortblade are always nonlethal. It's the same way here; the game would be harder if enemies could perform lethal animations against Altair.
Now here's a flaw in the guard combat system. The guard being attacked won't fight back while the other is attacking him because he is too busy fighting Altair. I found this can be fixed if Altair isn't in his line of sight while he is being attacked. Then he will retaliate against the other.
Final Thoughts
When AC2 was coming out, I saw a video where a developer stated that there were other features they wanted to implement for AC1, but didn't have the chance to. It stands to reason the existing combat between enemies is one of those features.
On Gamefaqs, there is a topic about making guards kill each other. It started with running around guards for accidental friendly fire, but went on to claims of intentional fights between enemies.
http://www.gamefaqs.com/boards/930022-assassins-creed/41882218
Yet another rumor proved true.
Damn. That is pretty impressive. Eight years later and now we know.
Incredible how much depth AC1 has to it, all these little touches that are so awesome to discover.
Shit mate, I never knew this behaviour even existed. Nice find!
How many more rumors are left? 
Is it possible to let them go kill the targets for us?
Is it possible to let them go kill the targets for us?
God I love this place.
Also, at about 3:20, when you get the templar to fight the regular guards.... does he... does he throw a (really ineffective) smoke bomb? 
“Force has no place where there is need of skill." Herodotus
There is quite a bit of history behind this. It started a few years ago when I was fighting a group outside of Abul Nuquod's palace. The leader swung at Altair, who was running out of the way, and next thing I know, he slashes down on another guard's shoulder and thrusts the blade through his belly. It was one of those did-that-just-happen moments.
So I look up online to see who else his happened to and found the Gamefaqs topic. One of the posters just happens to be out very own Jack Reacher.
I tried to make it happen again by turkey shooting a guard and getting another to attack in that direction, with no luck. But sometime later I got a break. After dying in the Maria assassination, I noticed a guard throwing another. That was really strange because although I've seen enemies accidentally hit each other, never a grab. So I died over and over again until it happened a few times, and noticed that both guards were always a Crusader and Saracen. *lightbulb goes off inside head* Later confirmed the possibility of different enemy factions by letting a Templar kill me in front of guards in Jerusalem/Damascus.
I theorized that if I could get a guard to kill another while Altair is anonymous, it could start a fight. Just to find the right place and situation. Abul's palace looked good because glitching inside from the back, Altair can walk over and go into ghost mode. Getting a cloned Templar over there was a big enough hassle.
Eventually the stars were aligned perfectly, and I glitched inside, fought against a Templar and Saracens, and moved out of the way, crossing the line that started recording the ancestors memory while the Templar accidentally hit a guard. And that is how I found out that the guards around the palace disappear at that point. 
As you can guess, I was discouraged and gave up on that. Another place I tried was near the entrance to Masyaf in kingdom (by where I fought the assassin guard and Saracens in the video), because in the area between the assassin guards and rest of kingdom, there are lines that cause Altair to become anonymous. One time one of the Assassins ran up to a Saracen chasing me and quickly killed him, but besides that I was unsuccessful. I remember Rob_88 mentioned in a topic that he had Saracens chase him there to see if they would fight the Assassins.
Then a few weeks ago, I was investigating something in the Talal assassination (never mind what I was investigating, heh heh heh. Oh, to heck with it. I was trying one of my ideas for an Early Death and failing.). Just fighting some guards in front of the entrance to the warehouse when a strolling Templar I had escaped from started attacking them.
I quickly paused the game and looked for a blank disk to record with. To my dismay, I didn't have any left. Just as well, because of how the Xbox360 works when you switch from HDMI to AV cables. I knew the console could restart in those situations, but was willing to take the chance. Sure enough, after I replaced the HDMI with AV cables and changed it to the appropriate channel, the Xbox360 restarted. This is one of them cases where the PS3 is superior.
But at least I had a lead. Hide behind a corner so the guards get seen, not you. Then the last piece of the puzzle was revealed: the guards will only get noticed if they are performing an illegal action. Attacking looks like the only action that counts; guards regularly knock each other off ladders if they're all climbing down one, an act that makes Altair instantly worthy of death.
If you'll notice the two references to controlling your opponents. First an brief scene for the Yugioh TV series (which I neither deny or affirm watching). The Brain Control magic card is played, a card that places one of your opponent's enemies on your side. Then the title of the video, Altair the Confessor. A confessor is a powerful being from a book series made into a TV show, Legend of the Seeker. I remember one of their powers is turning an enemy into an ally in battle. Back when I was regularly larping, we had a type of battle in which someone from both sides can "confess people".
Here's what a confessor's dress, um, robe looks like (I think all confessors are women):
Eight years later and now we know.
Almost eight. AC1 was released in Nov 13 2007.
Is it possible to let them go kill the targets for us?
Speaking of my next video... Yes, targets (not sure how many) can be killed without Altair having to lift a finger. I've tested on some targets, and either they have a *beep* ton of health or it might just take high level guards to kill them, because the regular guards can't do it, even after so many hits. Perhaps Al Assass can use Cheat Engine to determine what's going on.
How many more rumors are left?
All I can think of right now is the skydiving assassination people have claimed to have done on William.
http://thehiddenblade.com/assassination-challenges
Also, at about 3:20, when you get the templar to fight the regular guards.... does he... does he throw a (really ineffective) smoke bomb?
And I thought the combo kill was awesome. No way that was just a portion of mist.
Speaking of my next video... Yes, targets (not sure how many) can be killed without Altair having to lift a finger. I've tested on some targets, and either they have a *beep* ton of health or it might just take high level guards to kill them, because the regular guards can't do it, even after so many hits. Perhaps Al Assass can use Cheat Engine to determine what's going on.
Damn! I'm so hype for it. 
I remember Rob_88 mentioned in a topic that he had Saracens chase him there to see if they would fight the Assassins.
this makes me so happy to see. i remember trying that, by using the part outside Masyaf where if you go Left you find a group of Saracens, but on the right is a squad of Crusaders (or the other way around)
i could never get it to work, though.
nice job