Author:Vampiresbane
Original Thread: Vampiresbane's Art of Diplomacy

Vampiresbane's Art of Diplomacy Guide Medieval 2's diplomacy has been accused of being horrendous, awful, and tends to be ignored, but if understood, you can use diplomacy to shape the world around your fledgling empire to great effect. Unfortunately the manual that comes with M2TW is almost devoid of any good guidance on how diplomacy works, but I believe I have figured out most all of the tricks!

Successful Diplomacy relies heavily on two factors: your Reputation within the world (basically how trustworthy you are) and your Relations (aka Standing) with each faction (how much they like you). I'll break down how these work with Diplomacy as well as other impacts on Diplomacy such as Alliances, War, Vassals, etc.

Chapter 1: Preventing Neutral Factions from Attacking You
Spoiler Alert, click show to read: 

First off let's go over Relations. They are hugely important and are the root of why neutral factions attack or stay at peace with you and why sometimes even Allies will betray you!

For the most part, if one or more conditions are triggered, a neutral faction will attack you.
#1 They have territory adjacent to you.
#2 One of your adjacent cities/castles is undermanned. (Sometimes ports can be attacked as well, having a few ships in each port can help with this.)
#3 They have a large army just waiting to cause trouble.
#4 Their relations to you are "So-So" or lower.
#5 Your reputation is "Mixed" or lower.
#6 You have been excommunicated.

In this case, you have control over 4 things. First, if you see your enemy building up forces next to your vulnerable cities, beef up those towns. It won't necessarily prevent them from attacking, but it does make you a less likely target.

Next make sure your relations are "Respectable" or higher. "Amiable" or "Good" are even better, but can be harder to get. Typically the higher your relations and standing, the less likely another faction will attack you. I usually try to maintain a standing of "Reliable" or "Very Reliable."

To control if/when you get excommunicated, basically you need to control relations with the Pope. If you keep relations with the Pope at "Amiable" or higher, every time he sends a quest warning to not attack a faction, your relations will go down with the Pope, but you won't get excommunicated. If you're at "Respectable" or "So-so," the next time you get a quest warning from the Pope, it will be with the threat of excommunication.

Sadly, there are times when there's nothing you can do to stop a faction from attacking you. You've taken care of everything you can, but they simply have no one else to attack so their empire can expand. So guess what? They're coming for your lands. But the above can help reduce the number of fronts you fight on as well as help manage what factions you do end up fighting. In this way, you can be ready for it, when they come.

I'll go over Reputation in a bit, but let's go over how to increase relations.

Levels of Relations
(from lowest to highest)

Abysmal
Terrible
Very Poor
Poor
So-so
Respectable (Basically Neutral)
Amiable
Good
Very Good
Outstanding
Perfect

(There's actually two levels of perfect, the game just doesn't display them. Using the Pope as a diplomatic example, "Super" Perfect is a set of full crosses whereas "Regular" Perfect is a full set of cross, minus one. Full set of crosses, minus two, is Outstanding.)


Chapter 2: Getting Relations Up
Spoiler Alert, click show to read: 

Gold is your friend and mine.
How can you get relations up you ask? Ah ha! On to one of my biggest discoveries. The diplomat's best friend, the 100 gold donation. For this you obviously have to have a robust economy and keep a close eye on neighboring faction relations. I will sometimes end up using a full turns worth of income to boost a neighboring faction's relation up to Amiable. Be wary, however, since this cash tends to be used to build bigger potential enemy armies.

NOTE: I've actually tested using larger amounts such as 1000g, but the boost/gold amount effect is greatest when using 100 gold increments. Somewhat tedious to do I realize, but nonetheless effective.

The offer the AI can deny, but boosts Relations.
Another way is to offer something the faction wants to accept, but just can't quite accept. This usually occurs when asking for a marriage alliance, military access, or peace if the enemy is bankrupt. In the first two cases, they want to accept, but their relations aren't high enough to do so. Just keep offering the marriage with the same terms (or military access) and if they keep saying "just rejected" and they seem happy, chances are their relations are going up. Toss in an occasional 100 gold donation just to make sure you don't get the dreaded bane of diplomats, "forget it, we're not interested..." and having all diplomacy ceased.

Asking for peace with an enemy faction that is low on cash or bankrupt can result in the same relation boost. For instance, the enemy wants to accept a Peace/Tribute of 1000g/10turns, but can't afford it, keep offering it. Their relations will go up and up. Once they're at perfect, check first to see if they'll accept vassalage (always, always see if a faction will accept vassalage at every opportunity), then concede peace with whatever they can do. Typically a bankrupt faction will at least pay 500g/5turns for peace. Voila now you're at peace with a faction that previously hated you and now loves you immensely. Now as long as your cities are well garrisoned that front should be quiet for quite some time.

NOTE: Another good hint that your declined offer is actually boosting Relations is if the AI is rating it as "Generous" or "Very Generous" and is still declining. Give the offer a few more times and you should see Relations go up.

NOTE: Do realize that the more 100 gold gifts you make, the better your diplomat's influence gets since each is a successful diplomatic action. For instance if you use a diplomat to sue for peace and then raise that faction's relations from Abysmal to Perfect, his influence will be near maxed once you're done. In contrast, the second strategy will completely destroy your diplomat's influence since every diplomatic action is refused (excluding the final action).


An Diplomatic Example
Learning when offering these non monetary agreements to boost relations is a bit tricky and takes some practice, but can be immensely beneficial and can save you loads of cash. For instance, I played a Vanilla M2TW game as HRE and wanted to both ally with France, get my princess married to their prince, and exchange military access. I recently had taken the castle of Metz. My diplomat offered a marriage and got it without any trouble, but France kept on declining military access, but relations didn't go down with the offer.

That's the first sign. If the faction actually wants the deal, relations will either remain stable or go up. If they don't like the deal at all, relations will go down. What we don't see in the background, is the relation numbers going up or down, but we can see the result by watching the effect on relations.

So I offered to give them Metz. They declined, but their relations went up. I then offered the exchange of military access. Relations remained stable, but I had a hunch they were inching up in the background. Alternated both offers and relations went up to "Very Good." Ah ha! I was right. They like both offers, but for whatever reason, they're declining. At this point, from experience, I could have offered a wagon load of gold for the military access, but I also knew that if I got relations to perfect, I could either get it for free or for much, much cheaper. I repeated this process until their relations were "Outstanding," gave them Metz after all (I didn't really want it), relations went up to "Perfect," asked for military access and they accepted!


Chapter 3: Keeping Reputation at a 'Reliable' level
Spoiler Alert, click show to read: 

In addition to Relations, Reputation or Standing plays a big part in how well diplomacy will work between you and other factions. Reputation basically is how much does the rest of the world believe that you will keep your agreements ie alliances, trade, peace, etc. Having a poor reputation means two things: #1 Getting agreements will cost more or be impossible. #2 Other factions will attack you more often.

Reputation has a similar hierarchy to Relations and I’ll list the levels here. If you want the nitty gritty details, I suggest going to www.twcenter.net/wiki/Reputation-M2TW, as it has everything listed that affects Reputation.

Levels of Reputation
(from lowest to highest)

Despicable
Deceitful
Very Untrustworthy
Untrustworthy
Dubious
Mixed (Neutral)
Reliable
Very Reliable
Trustworthy
Very Trustworthy
Immaculate

Typically you'll want to keep Reputation to "Reliable" or "Very Reliable" if possible though I have heard of players still getting Vassals or Peace agreements with "Untrustworthy" Reputations. From personal experience, the worse your reputation is, the harder it is to get agreements and/or it will be more expensive.

The TWC wiki does list what affects Reputation, but I’ll give a quick overview of what you should worry about the most.

#1 Never, ever gift a region to a faction and then take that region back.
#2 The more Alliances you have, the higher your reputation.
#3 The more factions you’re at war with, the lower your reputation.
#4 Breaking any agreements, including when one ally attacks another thus breaking one of your alliances, hurts your reputation.
#5 Releasing prisoners increases reputation while executing hurts reputation. If a noble is involved, affects are increased.
#6 Occupying increases reputation while sacking and exterminating hurts reputation.

I am guilty of #1 and it quite literally ruined a game for me. I was playing as Venice and had two Vassals at the time, France and HRE. Early on in my campaign I had taken Jerusalem from Egypt in a crusade, restored order, fixed the place up, and gifted it back to Egypt. Because I no longer had any adjacent territories, I got a very lucrative peace agreement with Egypt (wagons of gold!), but 100 years later, I had forgotten my earlier crusade. I retook Jerusalem and my reputation fell through the floor. I went from “Very Reliable” to “Deceitful” in that one single move. Because I hadn’t figured out why my Reputation was so bad and how hard it made diplomacy from that point on, all my saves were post Crusade Numero Dos. I had to restart.

#2 and #4 are hard to juggle sometimes. While having as many alliances as possible, increases your reputation, it increases the risk one of your allies will attack another ally, thereby hurting your reputation. As a rule of thumb, I generally only set up 2 “risky” alliances. That way, if I’m sitting at “Reliable” or “Very Reliable,” worse case scenario, I’ll end up at “Mixed” or “Dubious” and I’ll still be able to get agreements through. Typically, breaking an Alliance can drop your Reputation by one level.

#5 and #6 In general, unless you’re shooting for “Immaculate” you can occasionally sack, exterminate, ransom, or execute. You’ll want to do it sparingly though. In general, I only sack if I’m about to go bankrupt or execute if the army I just captured would be a big threat if allowed loose once again. Oh and for those trying to get "Immaculate," I wouldn't recommend playing on Very Hard. Because of game mechanics, your Reputation continuously takes a hit, making "Immaculate" on Very Hard nigh impossible. Read the TWC wiki link for more info.


Chapter 4: Using Diplomacy and Alliances to Your Benefit
Spoiler Alert, click show to read: 

Big tip. You can actually use a set of enemy alliances for your benefit. I’ll explain after I go through the general rules of gaining an alliance.

You can increase the chance that you’ll get an alliance by:

#1 Being at war with faction your potential ally is already at war with.
#2 Not having adjacent borders.
#3 High Relations and/or high Reputation.

Benefits of alliance(s):
#1 One less front to have to fight on.
#2 Potential help with current enemy. (At the very least, your ally can help keep that opponent busy.)
#3 If your ally is allied with another one of you allies, if you increase your relations with one ally, the other relations will automatically go up.
#4 If one of your enemies is allied with another faction (neutral or enemy), and your relations go down or up with that enemy, the 2nd faction will likewise decrease or increase their relations with you.
#5 Ally relations typically stay at “Amiable” or “Good” without any diplomatic maintenance.

Most of the above is self explanatory, but I’ll go over #3 and #4 since they can greatly help or hurt you. #4 is actually a very big reason why you can find yourself suddenly fighting 6 or 7 different factions. Guess what, they’re probably all allies and if you are winning a war versus one (and as a result, your relations are going down with that faction), his allies are going to like you less and less until they’re relations with you drop to “So-so” or lower and guess what…you’re now fighting another faction.

The good news is you can actually use this enemy alliance tie to your benefit. Let’s say you’re the Holy Roman Empire (HRE), and you’re fighting Venice who’s allied to Hungary. Hungary isn’t at war with you…yet, but your relations are going down. You also are tired of fighting Venice. You boost your relations with Hungary with 100 gold gifts until your relations are “Good” or better. You end diplomacy, and, how ‘bout that, Venice’s relations with you went up as well. Not as much as your target faction, Hungry, but that’s less cash you’ll have to spend to make Venice happy enough to sue for peace.

The same technique can be used on your allies (if they’re allied with each other) and you want to get really good relations (rumor is that having perfect Relations with allies increases Reputation). Max one to “Perfect” and chances are, the 2nd ally who was sitting at “Good” will now jump to “Very Good” or even “Outstanding” for free.

NOTE: Want to know how to get a marriage alliance with an Orthodox faction if your faction is Catholic? Have your princess conduct diplomacy and ask to merry their prince.

NOTE: Another big tip is if you attack an ally of an ally, you'll almost always lose your direct ally. If you want to keep that alliance, goad their ally (that's not yours) into attacking you by pissing them off as much as possible and leaving a city pretty unprotected. Most of the time if your reputation and relations are high, if you were defending and were attacked, your alliance will hold.

An example for the above, you're allied to France who allied to Denmark, but you are neutral with Denmark. If you attack Denmark, France will probably break their alliance with you, but if you get Denmark to attack you, you'll probably get to keep your alliance and the Denmark/France alliance will break.


Chapter 5: Using Diplomacy to Start Wars
Spoiler Alert, click show to read: 

There’s a couple different avenues you can do to get a faction to attack you, even allies, though if you’re reputation is good, that’s actually harder to do. All of the following will decrease Relations.
#1 If the target faction is allied with someone, piss that someone off. (Indirect)
#2 Have your diplomat suggest absolutely absurd offers such as huge tribute. (Direct)
#3 March an army, large or small, around in their territory. (Direct)
#4 Break agreements with that faction. (Not recommended, also hurts Reputation)

#1 tends to be less effective, but can work. #2 is the one I generally use when trying to provoke a faction to attack me, but remember that if you offer the faction two offers in a row that he doesn’t like and refuses, he’ll stop negotiations. If you want to do #2 in one sitting, you’ll actually have to give 100 gold between the atrocious offers (or any other reasonable diplomatic offer).

Marching an army in the faction’s territory will work, but takes many more turns generally to really destroy a relationship. #4 works really well with current allies, but puts a dent in your reputation; use with caution.

Doing options 1 through 3 can even lead to your ally betraying you.


Chapter 6: Why Some Allies Betray You
Spoiler Alert, click show to read: 

You’ve done did it now. You either royally ruined Relations with your ally (ie walked in his territory for years without asking for military access), broken numerous previous alliances, and/or have terrible Reputation.

I’ve more or less gone over how to ruin Relations and Reputation. If your ally has betrayed you, chances are, your Relations and/or Reputation are down right terrible. Keeping Relations high with an Ally isn’t too difficult. It takes much less maintenance (ie cash) than keeping a neutral faction’s Relations high. However if you’re not careful, an ally will betray you if you have awful Reputation. Maintaining both will help keep your alliance strong. That is…if you wanted to keep it…


Chapter 7: Using the Excommunication System Against Other Factions
(Or how to use the Pope to 'lawfully' attack anyone.)
Spoiler Alert, click show to read: 

In order to use the Excommunication system to your advantage, you have to manipulate the Pope. Relations with the Pope work a bit differently than other factions.

Ways to Increase Papacy Relations:
#1 Join a crusade
#2 Complete a successful crusade
#3 Build churches
#4 Have a priest promoted to Cardinal
#5 Have a Cardinal become Pope
#6 Wage war against Islamic factions

Actions that have no effect on Papacy Relations:
#1 Defending an attack by another Catholic faction
#2 Attacking Orthodox factions (However attacking Orthodox factions while on a Crusade will decimate your papal relations-Constantinople is a great example. Generally, however, it won't hurt relations.)

Ways to Decrease Papacy Relations:
#1 Attacking Catholic factions
#2 Voting for the wrong Cardinal
#3 Other regular diplomatic routes such as trespassing in his lands or making poor diplomatic offers
#4 Attacking Orthodox factions while on a crusade, especially the city of Constantinople, severely hurts relations with the Pope.

For every faction, the Pope will give out warnings about either a dip in Relations or an excommunication if you attack other Catholic factions. Your relations with the Papacy make a world of difference between how badly your Relations go down or if you get excommunicated instead. The rule of thumb when attacking Catholic factions is if you’re at “So-so” relations or lower, don’t attack another Catholic faction. If you do, the next turn, you’ll receive a quest warning to cease your attack or face an excommunication. This can be avoided by using siege weapons such as catapults or trebuchets so you attack in one turn, but you’ll still have to stop any aggressive moves from that point forward (for at least 7 turns).

These rules apply to your enemies as well. It’s why Relations are so important with the Pope. If your enemy has really high Papal Relations and you don’t, he can attack you until his arms fall off and the Pope won’t excommunicate him. But if you’re enemy has really low Papal Relations and you’re at “Respectable” or higher, as long as you always defend against your enemies attacks, the Pope will excommunicate that enemy very soon. Then the fun can really begin. At “Outstanding” or higher Relations, you can actually call a crusade against your enemy. In this way, you can start moving large, very cheap armies (once paid for), and take multiple cities as long as you march each army in the general direction of the final city. I’ve completely taken out faction in two turns with this, a good example being Sicily where I sent 3 armies to Naples, Palmero, and Tunis with Tunis being the ultimate prize. In the next turn I took each city, wiped Sicily from the map, and was given “Perfect” relations with the Pope.

NOTE: One side note that’s a bit unrelated to this topic. Keep in mind Jihads can be called on Catholic and Orthodox factions, but Crusades can only be called on Excommunicated Catholic factions or Islamic factions.



Chapter 8: How to Sue for Peace
Spoiler Alert, click show to read: 

I actually discovered the AI's priorities by accident while trying to find ways to force the AI to accept a vassal offer using cheats. That and I have a certain fascination with the diplomacy system in this game so I enjoy changing each offer little by little to see where the cutoffs are.

Ultimately the AI likes cold hard cash. And not in the tribute form. Offers with the same overall amount offered in a single exchange are valued higher than the same amount given over time in the form of a tribute. Using the cheat cash code I used to force factions to accept Vassalage, I could offer 1,000,000 in one go or that much over time. Guess what. No matter how I altered the amount of turns I gave 1,000,000 gold over, it was refused every time. But if I offered it all at once, the faction would accept the offer of Vassal.

Now apply this to regular gameplay, if you're suing for peace or trying to get a vassal through normal means, the larger the upfront offer is, the better your chances are. The nice thing about M2TW is that the AI will have a reaction displayed at the bottom of the diplomacy screen so you can tell if your offer has a chance. "Very demanding" means you're pretty far off. "Demanding" means your offer isn't far off, but it needs to be better before being accepted and finally "Balanced" means you have a really good chance of being accepted. "Generous" or "Very Generous" has an even better chance of being accepted.

To increase chances of a Faction accepting Peace, you can do the following:
#1 Gift any regions that are currently making you have an adjacent territory. If you no longer have an adjacent territory, the AI will immediately want Peace.
#2 In general the better your Relations, the better chance you can sue for Peace and usually for a lower amount of money. (If you've been at war, Relations will usually be Abysmal. Boost them up if need be.)
#3 Wait until the faction has been excommunicated and/or many factions have declared war on it.
#4 Start destroying their funding sources and/or armies. The lower their "Wealth" and the lower their "Strength," the more likely they'll accept Peace and possibly even Vassalage.

NOTE: Most Vassals offers I've had accepted occur when I've either taken very little settlements from the faction, the faction is at war with many different factions, or if the faction is down to one region and is "Weak"/"Very Weak" strength and is "Bankrupt." If an enemy diplomat approaches you, you also have a higher chance of getting them to accept Vassalage.

NOTE: Also if a Jihad has been called against one of your cities, the initial Peace offer from the Islamic faction is the only one you get. If you try to counter with Vassal, both the "Peace" and "Vassal" option will disappear as options.

Tip: The fact that the AI likes bigger payouts upfront can work to your advantage since they're actually willing to pay you more in the long run than initially. This option does have a downside, however. If the faction breaks his peace agreement, he will no longer being paying you tribute. Overall, pay more upfront to get a hard offer accepted and if an offer is being made to you, ask for more money over time.


Chapter 9: Weird Things the Diplomatic AI will do
Spoiler Alert, click show to read: 

There's two set of items that the Diplomatic AI will do that just strike me as odd, but happen nonetheless and sometimes in the player's favor.

Weird thing #1
The first is the following situation. You're suing for Peace or offering some other agreement and you put forth an offer of 1000 gold/10 turns. The AI's reaction is "Demanding." You only have 1000g to give though since you only have 1000g in your treasury. So you offer 1000g/20 turns. "Very Demanding" What? That doesn't make sense. Raise it to 30 turns, "Very Demanding." 16 turns, "Very Demanding." 12 turns, "Demanding." 5 turns, "Very Demanding." If you're like me, you're left scratching you head and puzzled.

There's a weird gray line during negotiations that hangs around the 10 turn to 15 turn mark for offering tribute in return for peace in which the AI actually gets more angry the more money you offer. This may happen in other situations, but this is the most common. Plus it doesn't always happen either. I've never figured out why, but ultimately it has something to do with the fact the AI like more money right away then over a long period of time. The only real solution is wait a turn and offer more cash per turn or more cash upfront.

Weird thing #2
The second has something to do with the AI changing its short term goal or a section in the Diplomacy screen called "Priorities." The four biggest are: Trade, Military, War, Peace. Most of the time, the AI will have "Unknown" displayed and so the player won't be able to tell what the AI wants. Sometimes when approached for diplomacy, the AI will show "Unknown" at first and then once an offer is made and declined, sometimes even a really good one, the goal will show "Peace." There's some trigger that makes the AI show its "Priorities," but I haven't figured out what. Bottom line when this happens, the AI has decided it suddenly really wants Peace and often will give the player even more tribute, settle for less tribute from the player, or finally accept Vassalage. For some reason, once the player can see the AI's priorities, getting offers accepted is much, much easier and almost always in favor of the player and his treasury if the player takes advantage.

A good way to get the AI to let its "Priorities" known is to offer either 100g as a trade, leaving the AI offer blank, or to trade map information for map information. If the AI is willing to show its "Priorities," it will decline and possibly give a counter offer but now the "Priorities" spot will show something other than "Unknown." It doesn't always work, but if you can get the AI to show its "Priorities," it will ease the diplomacy process.


Chapter 10: Actual Point Values for Reputation and Relations
Spoiler Alert, click show to read: 
Reputation
Spoiler Alert, click show to read: 

Reputation is a number ranging from -1.0 to 1.0 with 0 being nuetral reputation or "mixed."

Positive factors
+0.0025 Alliance (Normalize reputation to 1.0 with divisor of 400. Initial bonus a single alliance has is +0.0025 or (1-0)/400)
+0.1 Attacking an enemy of an ally on land or at sea.
+0.01 Releasing less than 80 prisoners from a single battle
+0.026 Releasing more than 80 prisoners from a single battle
+0.025 Releasing an enemy general (captains don't count)(If you release more than 80 prisoners AND an enemy general, your reputation will go up by +0.051)
+0.05 Occupying a settlement*

*Currently bugged unless you patch your game with this file (file developed by taw); follow the instructions here

Neutral factors
-0- Ransoming prisoners (though TWC wiki once listed ransoming prisoners as giving a slight penalty; I can't seem to find this reference anymore)

Negative factors
-0.00125 Being at war. Normalises your faction's reputation to -1.0 with a divisor of 800. Initial penalty shrinks over time.
-0.1 Nullifying an alliance through diplomacy.
-0.1 Breaking an alliance. Occurs when two of your allies go to war and you have to choose which alliance to uphold.
-0.15 Breaking a trade or military access treaty.
-0.15 Bribing a settlement with your diplomat.
-0.5 Attacking an ally
-0.01 Executing less than 80 prisoners from a single battle*
-0.026 Executing more than 80 prisoners from a single battle
-0.025 Executing an enemy general, regardless of the amount of characters. (If you execute more than 80 prisoners AND an enemy general, reputation will go down by -0.051)
-0.02 Sacking a settlement
-0.05 Sacking a settlement while a faction is a horde (Mongols and Tumurids only)
-0.05 Exterminating a settlement
-1.0 Stealing back a settlement. Occurs after physically taking back a settlement with the use of force after giving the region away through diplomacy.

*Note that if you want a dread general this is the best choice with the least impact on Reputation


Additional factors
  • After each turn, the game will normalize your faction's reputation with a divisor of 200.
  • On Easy difficulty, reputation is normalized to 1
  • On Medium difficulty, reputation is normalized to 0
  • On Hard difficulty, reputation is normalized to -0.5
  • On Very Hard difficulty, reputation is normalized to -1.0

Miscellaneous
As TWC wiki points out, a common misconception is that using spies/assassins will lower your reputation. Using spies lowers your relations with other factions, but does not directly affect reputation. Using assassins, as long as you don't get caught, has no effect on reputation, but if you get caught and you're not at war, a captured assassin from a failed assassination attempt will cause war which does affect reputation (-0.00125). The Chivalry or Dread of your Faction leader also has no direct bearing on reputation (though his actions that made him Chivalrous or Dreadful can, depending on what they were).

Relations
Spoiler Alert, click show to read: 

Relations is a number ranging from -1.0 to 1.0 with 0 being nuetral relations or "reasonable."

Positive Factors
+0.2, normalization to +1 (divisor 20/turn) Princess married to faction heir
Small bonus for having the same religion (unknown value)
Allies grow to like you more (unknown value, probably normalized to +1 with some divisor)

Neutral Factors
-0- Merchant aquistion, Princess stealing generals, and priests preaching on foreign soil

Negative Factors
-0.5 to -1.0 with divisor 20 (divisor 80/turn for allies) Captured spy
Acts of Sabotage (unknown value)
Bribing (unknown value)
Assasination (unknown value)
Acts of agression (taking city, attacking armies, attacking navies) (unknown value)
Enemies grow to like you less (this occurs even without attacks or any of the above)


Additional Factors
  • After each turn, the game will normalize your faction's relations with a divisor of 200.
  • On Easy difficulty, relations is normalized to 1
  • On Medium difficulty, relations is normalized to 0
  • On Hard difficulty, relations is normalized to -0.5
  • On Very Hard difficulty, relations is normalized to -1.0
  • Factions with high reputation get liked more, factions with low reputation get liked less. Thresholds are (-0.4, -0.1, +0.1, +0.4) and also normalized each turn.
  • Factions with higher military strength get liked less (unsure of amount); factions which are weak get liked more.

Papal Relations
Spoiler Alert, click show to read: 

This deserves its own section, not only because the Pope gets his own relations code, but because the politics of the Papacy have such a large effect on Catholic factions.

Positive Factors
+0.02 to +0.2 Built small church/chapel to huge cathedral
+0.2 Built first huge cathedral in the world
+0.2 Built faction's first huge cathedral

Bonus for attacking Islamic faction (in general, doesn't have to be a crusade)
Bonus for every general and every unit in crusade (unknown value)
Bonus for arriving at target region while on crusade (unknown value)
Bonus for taking target region while on crusade (unknown value, but fairly high)
+0.2 If Heir is sent on crusade
+0.6 If Leader is sent on crusade

Bonus for recruiting priest (unknown value)
+0.1 Priest promoted to Cardinal
+0.2 Voted for Winning Pope
+0.4 Allied Cardinal elected Pope
+0.8 Your Cardinal elected Pope

Neutral Factors
-0- Defending an attack by another Catholic faction
-0- Attacking Orthodox factions (in general; in contrast if you're on a crusade, it severely hurts Papal relations)

Negative Factors
-0.10 to -1.0 Destroying small church/chapel to destroying huge cathedral
-1.0 Attacking Orthodox faction while on Crusade (taking Constantinople on the way to the Holy Lands)
Penalty for being at war with Catholic factions (unknown value)
Penalty for heretics in your lands (unknown value)
-0.2 Pope appoints an Inquisitor in your lands
-0.4 Enemy Cardinal elected Pope



Conclusion

Thanks for reading and I hope this really helped other players sort out the diplomacy better. For a long time I never understood it and it was quite confusing. I'll be editing this to fix grammar and to take out American cliches so Google Translate will work better for Non English readers, but ENJOY!

Other good diplomacy guides:
http://www.twcenter.net/forums/showthread.php?t=225712
http://www.gamespot.com/pc/strategy/...&mode=previews
http://t-a-w.blogspot.com/2009/11/wh...edieval-2.html Has actual point values for Relations.
http://www.twcenter.net/wiki/Reputation-M2TW Has actual point values for Repuation.