Diplomacy in Warhammer 2 is mysterious, limited, and often frustrating. Here are the insights for how diplomacy works I have found to empower you to squeeze every advantage you can while avoiding terrible scenarios.
Guide to Diplomacy in Warhammer II
Beware of Alliances
If you have a Defensive Alliance with 2 factions, and 1 of those factions attacks the other, either way you are going to suffer a negative hit to your reliability; if you join the defender then you will declare war on the attacking ally, which is a nasty hit, especially if you had other treaties with them. If you decline the defender, you suffer a hit.
A Defensive Alliance is not as bad as a Military Alliance in this regard, because if a Defensive Ally attacks a faction you have a trade agreement, military access or non-aggression pact with, you are not obligated to assist either of them (and you will not even be prompted to)
A Military Alliance is even worse. If a Military Ally attacks a Defensive Ally, whichever choice you make will cause a hit for failing to join your ally, whether attacking or defending. But also, if your Military Ally attacks a faction you do not have a Defensive Alliance with but you do have 1-3 of the other treaties (non-aggression pact, trade agreement, military access), you suffer a hit if you fail to join your Military Ally (and failing to join your ally may break the Military Alliance causing another hit, especially if 10 turns have not passed since you signed the alliance), but if you attack a faction you have treaties with, you will suffer a heavy reliability hit there too.
So you are safe just doing non-aggression pacts, military access and trade agreements as long as you do not attack the faction you have treaties with, and be sure to cancel all the treaties and wait 10 turns before declaring war on them if you do end up deciding to attack them.
Join War Tricks
Here are some nice tricks for using "Join War" for your benefit.
You can request money from the AI when offering to join a war against one of their enemies. So if you need some cash, you can offer a wealthy faction your aid in their war against an enemy for as much money as you can squeeze out of them.
If you fight an AI faction's enemies, they tend to like you. So if on the Vortex map you are Malekith and you want Kroq-Gar on the opposite side of the world to like you (maybe you sent an agent down to discover him and trading with him would provide a great income if you could get him to accept a trade agreement), you could offer Kroq-Gar to declare war on Clan Mors, Clan Moulder, or some other faction near him that he is at war with. Since it is unlikely you will have to fight your newly-created enemy, it's like free favor man.
Let's say you want to declare war on a faction, but that faction is Defensively or Militarily Allied with another faction that you really do not want to go to war with, here is nice trick. See if anyone else is at war with the faction that you want to fight, and offer to Join War against your enemy with whoever that faction is. This will allow you to get into a war with your desired enemy without prompting their ally to defend them. Now their ally may eventually attack you if they decide they do not like you on their own, but hopefully that will be further down the line once you are in a better position.
How Reliability Works
I really want you to pay attention to:
You cannot see the negative points values during your gameplay, all you can see is if you hit "Very Low" Reliability. So you could have just dipped below "Very Low" and be back up to Low, Medium, High, Very High reliability in a short number of turns; or you could have betrayed so many pacts that your rating will be so low, it will be well over 100 turns before you even come close to rising even just to low reliability.
Simply canceling a treaty can cause a 10 point hit per treaty to your reliability; so if you cancel 3 treaties with a faction in preparation to attack them after 10 turns have passed (so you do not suffer all the negatives listed below), you still could have suffered a gnarly hit to your reliability. Now perhaps you cancel 3 treaties with multiple factions at once in preparation for "Total War", you might suffer quite a large penalty.
This is just from my own experience - if you wait until 5-6 turns have passed after ending all treaties with a faction, and then declare war, the hit to your reliability may not be as harsh. You'll get hit, but if you really need to attack a faction, if you can wait 5-6 turns before doing so, the hit may not be as harsh.
"It's easy to get to a 'very low' rating, but in two different situations you can have 'very low' reliability but your hidden actual score is radically different. Because there is no lower bound to the score. Meaning in the one case you are just barely in the hole, and recovering some reliability points every turn, so return to reliable levels fairly quickly. While in the other case your score is at the bottom of the ocean and will take a hundred turns or more to recover.
How exactly the points add up and how many you recover per turn is unknown, I think. But some things can be learned from the database. Treacherous acts will give you points, so technically you never have a reliability score, you only have an unreliability score; if you are reliable you are at zero, and every point above zero makes you less reliable.
- Refusing to join an ally in war adds 15 points.
- Cancelling a Military Alliance before the 10 turns have elapsed is 10 points.
- Cancelling Military Access is 10 points.
- Going to war shortly after cancelling military access is 15 points.
- Declaring war after ending a military alliance without waiting 10 turns is 25 points.
- Declaring war again shortly after signing a peace treaty is 30 points.
- Cancelling trade is 10 points.
- Going to war after ending trade is 15 points.
- Making peace after less than 10 turns of war is 15 points (this may seem odd but if you just make peace without any serious fighting this would rightly be seen as a betrayal by your partners in that war).
Like I said these points seem to all add up. So if you were allied with a faction and also had a trade deal, and then first refuse to join them in a war, then actually declare war on them, you will be hit with a MASSIVE blow to your reliability:
- +15 from refusing to join their war.
- +10 for cancelling alliance if it was still new.
- +10 for cancelling the military access.
- +25 for declaring war shortly after ending alliance.
- +15 for going to war shortly after ending access.
- +10 for ending trade if it was a fresh agreement.
- +15 for going to war shortly after ending trade.
So that is +100 unreliability for what may seem to you like 'only' a single betrayal.
You can significantly reduce the impact if you are willing to at least wait 10 turns: End all the agreements immediately, but wait the 10 turns after that before declaring war. Then it's only:
- +15 from refusing to join their war.
- +10 cancelling alliance.
- +10 cancelling access.
- +10 cancelling trade.
So that's 45, less than half. While you may think 'okay I'm unreliable now anyway, now I can just do to them what I want, it doesn't matter", actually it does matter. Limit your betrayals as much as possible to be able to recover from them more quickly."
Make Diplomacy Pay You
You can ask for money when offering treaties, you can ask for money when offering to join a war, you can ask for money when asking a faction to confederate with you (they are giving you their cities and armies, might as well give you their treasury too).
If you have lots of treaties with a faction and they are "Green" with you (really like you), you can ask them to give you money without offering anything, and every so often they will accept, just giving you some money. Often it is just 300 gold, but I've even seen 1300 and occasionally 2300 gold given.
You can adjust the amounts you offer or request from the AI. This is particularly useful if say, it seems like they will easily accept paying you 800 gold, but they definitely will not accept paying you 2300 gold. Maybe they would pay you 1300 gold? You can definitely play around with it and see what you can get out of the AI and when, it is just annoying have to do repeatedly take shots in the dark as to whether the AI will accept or not, which is why so many hate diplomacy, and I've read that is why 3K's diplomacy is considered a huge improvement, because it is not so mysterious.