The Mechanics of Territorial Cession

If you are not persuing a domination victory,the deplomatic penalty of declaring war as well as capturing cities is somewhat bitter to bear in BNW,especially in the early stage.Why do we start a war?Mostly to expand territory.The aftermath of conquering cities is severe: population halved,buildings destroyed,and reputation stained.So why not try a peaceful way?We know that AI sometimes give in their cities if the war is not in their side.But we don't know exactly how they make their judgement-sometimes AI would rather die than submit,sometimes they give in just so easily.So,let's figure this out.

I.Definition of parameters:
P(peacetreatywillingtooffer):how much AI would be willing to give in a peace treaty

WS(warscore):how well the war is going for AI
AMP:AI's military power
PMPlayer's military power
MS(MilitaryScore)layer's relative mitary power comparing with AI
WT(WarTurns):Turns this war has endured.

AEP:AI's economic power
PEPlayer's economic power
ES(EconomicScore)layer's relative economic power comparing with AI

APL:AI's property lost in this war
APR:AI's property remaining in this war
ARL:AI's relative lost in this war
PPLlayer's property lost in this war
PPRlayer's property remaining in this war
PRLlayer's relative lost in this war

PC: percentage of cities AI willing to give up
CVM:city value modifier

II.Mechanics:

P and MS are originally 0.
To calculate WS(Warscore）,AI first consider military power of both sides:
power of military unit=basic combat(ranged unit uses ranged combat)*(1+0.125*unit's level)*unit's current HP/100
AMP=MA=30+Total power of AI's military units*[1+√（AI's Gold）/100]
PMP=MA=30+Total power of Player's military units*[1+√（Player's Gold）/100]
MS=PMP/AMP
If:
MS>=2.5 WS reduces by 100 elseif
MS>=1.65 WS reduces by 60 elseif
MS>=1.15 WS reduces by 25 elseif
MS>=0.8 WS reduces by 0 elseif
MS>=0.6 WS increases by 25 elseif
MS>=0.4 WS increases by 60 elseif
MS<0.4 WS increases by 100

Then consider economic power:
AEP=AI's total population+AI's total production(from tile,building,policy,trade route)+AI's total money yield(from tile,building,policy,city connection and trade route)
PEP=Player's total population+Player's total production(from tile,building,policy,trade route)+Player's total money yield(from tile,building,policy,city connection and trade route)
ES=PEP/AEP
If:
ES>=2.5 WS reduces by 50 elseif
ES>=1.53 WS reduces by 30 elseif
ES>=1.2 WS reduces by 12 elseif
ES>=0.83 WS reduces by 0 elseif
ES>=0.65 WS increases by 12 elseif
ES>=0.4 WS increases by 30 elseif
ES<0.4 WS increases by 50

Then consider war damage:
APL=total power of AI's lost military units*100/the highest combat among all AI's available military units+total population of AI's lost cities except the capital*150+population of AI's capital(if it has fallen)*225
APR=total power of AI's remaining military units*100/the highest combat among all
AI's available military units+total population of AI's remaining cities except the capital*150+population of AI's capital(if it has not fallen)*225
ARL=APL/(APL+APR)*100
PPL,PPR and PRLare calculated likewise.
If:
ARL=0 and AI believe player is aggresively expanding W increases by 25 elseif
ARL>=10 WS reduces by 10 elseif
ARL>=25 WS reduces by 20 elseif
ARL>=50 WS reduces by 30 elseif
ARL>=67 WS reduces by 40

If:
PRL>=10 WS increases by 5 elseif
PRL>=25 WS increases by 10 elseif
PRL>=50 WS increases by15 elseif
PRL>=67 WS increases by 20

At last,consider how long the war has been going:
If:
T>60 WS reduces by 20 elseif
T<=60 WS reduces by(T/3)

Now calculate P:

P is influenced by MS,ARL and PRL

If:
WS<=-100(Destructive) P increases by 100 elseif
WS<=-25(Defeat) P increases by 60 elseif
WS<= 0(Stalemate) P increases by 20 elseif
W>0(Unknown) P increases by 0 elseif
W>=25(Good) P reduces by 20 elseif
W>=100(Very Good) P reduces by 50
If player is a terrible target for AI,change Warprojection Destructive and Defeat to Stalemate.

If:
ARP>=10 P increases by 10 elseif
ARP>=25 P increases by 20 elseif
ARP>=50 P increases by 50 elseif
ARP>=67 P increases by 80

If:
PRP>=10 P reduces by 10 elseif
PRP>=25 P reduces by 20 elseif
PRP>=50 P reduces by 50 elseif
PRP>=67 P reduces by 80

Now AI proposes a peacetreaty depending on P:

White peace:AI gives up nothing
P<20

Armistice:AI gives up 50% Gold and 50% GPT
P>=20

Settlement:AI gives up all Gold and GPT
P>=40

Backdown:AI gives up all Gold,GPT and all strategic resources,open borders
P>=55

Submission:AI gives up all Gold,GPT,all strategic and luxury resources,open borders
P>=70

Surrender:AI gives up one city
P>=95

Cession:AI gives up 25% cities(PC=25%) and 50% Gold
P>=120

Capitulation:AI gives up 33%(PC=33%) cities and 50% Gold
P>=150

UN-Surrender:AI gives up all cities except capital(PC=100%) and all Gold
P>=180

If player has broken a peacetreaty with this AI before,AI will give up nothing.
eg:
promise another player to declare war on this AI after 10 turns.
declare war on this AI and make peacetreaty in 10 turns.
keep promise and declare war on this AI after 10 turns.

Which cities AI choose to give up:

Firstly,sorts all AI's cities except capital based on their distance to player's capital,from proximal to distal,adds them into a queue.If a city is founded player,divide distance by three.

If AI gives up only one city,will choose the closest one.

If AI gives up more than one city,calculates total value of AI's cities,multiply it by PC,and the result is the limit of how much city value AI is willing to give up.
AI will add in cities from the queue one by one if not surpassing the limit.
If the value of the first city hits the limit(When AI has few cities or the one closest to your capital worths the most),AI won't give up any city.

How AI calculates the value of a city:

basic city value=440+population*200+&#65288;tiles+0.25*improved tiles-7&#65289;*tile cost+total luxury value(equals the cost we pay for them in a fair deal. value per copy=dealturns*happiness provided*2,tripled if unique,240/720 in standard speed)+total strategic value(90 per copy)

tile cost=&#65288;50+5*tiles already purchased&#65289;*&#65288;1+Policy/Traits/Wonder modifier&#65289;.Tile cost doubled if it belongs to a minor civ(not happen in this case)
(Bad news for Washington...)

city value is also influenced by war:
Warprojection CVM
destructive 1
defeat 1.8
stalemate 2.2
unknown 2.5
good 4
very good 4

CVM=2 if player and AI are in peace

city value=basic city value*CVM

How AI assesses a player as a terrible target:
[edit]

I have some questions,if P is negative would the proposal be symmetric to positive P's?(except that of course now the player is the cession side)
What is the threshold that the AI will be willing to negotiate peace at all?

Ronza149 said:

I have some questions,if P is negative would the proposal be symmetric to positive P's?(except that of course now the player is the cession side)
What is the threshold that the AI will be willing to negotiate peace at all?

Click to expand...

There is another P(PeaceTreatyWillingToAccept) determines how much AI would like to demand from you.Whether AI would be willing to negotiate peace depends on its wargoal,if AI wants to wipe you out of the planet there is no peace.AI changes its wargoal depending on how the war is going.

Fallen_Kings said:

There is another P(PeaceTreatyWillingToAccept) determines how much AI would like to demand from you.Whether AI would be willing to negotiate peace depends on its wargoal,if AI wants to wipe you out of the planet there is no peace.AI changes its wargoal depending on how the war is going.

Click to expand...

Could you briefly talk about how war goal is measured?based on my experience it must be strongly related to the relative military power.

Ronza149 said:

Could you briefly talk about how war goal is measured?based on my experience it must be strongly related to the relative military power.

Click to expand...

Later.It's mainly related to power and distance.

Fallen_Kings said:

If player has broken a peacetreaty with this AI before,AI will give up nothing.
eg:
promise another player to declare war on this AI after 10 turns.
declare war on this AI and make peacetreaty in 10 turns.
keep promise and declare war on this AI after 10 turns.

Click to expand...

Being able to break a peace treaty the same turn I make it like that is working as intended? I always thought it was a bug.

What other ways can I break a peace treaty?

Magma_Dragoon said:

Being able to break a peace treaty the same turn I make it like that is working as intended? I always thought it was a bug.

What other ways can I break a peace treaty?

Click to expand...

Defensive Pact comes to mind.

I have noticed that if the AI is willing to accept peace at all, even if they feel they are in a dominant position and would demand you give up everything you own for peace, they'll just accept a neutral peace treaty anyways.

ravenmagus said:

I have noticed that if the AI is willing to accept peace at all, even if they feel they are in a dominant position and would demand you give up everything you own for peace, they'll just accept a neutral peace treaty anyways.

Click to expand...

Me too. I feel like this is new after the patch from a month or two ago, and was wondering if it was a bug.

super super userful. thanks. please keep making posts like this.

A question for the OP. How is the base War score calculated? 0? (EDIT: I meant to say, how is the war score initially calculated? Is it set to 0?)

Never knew that your gold plays such a big role here. Also, is "money yield" just the gold being generated not including the gold per turn you are paying to other civs? For example, if you are generating 100 gold from tiles/religion/policy but you are paying other civs 100 gpt, is the yield 0 (or 100)?

TheGrumpyBuddha said:

Me too. I feel like this is new after the patch from a month or two ago, and was wondering if it was a bug.

Click to expand...

Same here. It must be bug.

My frustration with this mechanic, in my experience, is that you can't ask an AI for its open borders. It has to suggest open borders in the peace treaty or you can't get them.

The problem with this is that I generally consider gpt and luxes to be worth more than cities. So when an AI decides it wants to give me a city, I can't ask for gpt/lux/open borders... I can only ask for gpt/lux.

BlackWizard said:

Same here. It must be bug.

Click to expand...

If you look at the OP, no P (peacetreatyoffering score) corresponds to a case in which AI requires you give him something in return. The worst case (for the player) is that the AI will make peace while unwilling to give up anything.

This may be the similar mechanic as normal trading scenarios. AIs will frequently ask for extra things. Sometimes, for example, when you ask for open border, friendly AI will ask for 10 additional gold. You can remove the gold (and not change anything else), and he will accept your offer. SOmetimes he will add on strategic resources (horse or iron) that he doesn't even want (based on his unwillingness to pay 1 gpt for them) and the trade will go through

YourHarry said:

If you look at the OP, no P (peacetreatyoffering score) corresponds to a case in which AI requires you give him something in return. The worst case (for the player) is that the AI will make peace while unwilling to give up anything.

This may be the similar mechanic as normal trading scenarios. AIs will frequently ask for extra things. Sometimes, for example, when you ask for open border, friendly AI will ask for 10 additional gold. You can remove the gold (and not change anything else), and he will accept your offer. SOmetimes he will add on strategic resources (horse or iron) that he doesn't even want (based on his unwillingness to pay 1 gpt for them) and the trade will go through

Click to expand...

You mean except for this part:

Fallen_Kings said:

There is another P(PeaceTreatyWillingToAccept) determines how much AI would like to demand from you.Whether AI would be willing to negotiate peace depends on its wargoal,if AI wants to wipe you out of the planet there is no peace.AI changes its wargoal depending on how the war is going.

Click to expand...

If the AI is dominating you in warfare and has tons of units to your small force they will sometimes demand cities from you for a peace treaty; you can see this when they come to you on their own turn for a peace treaty. The fact that they will accept a neutral peace treaty instead does seem like a bug.

The trading oddity is an entirely different affair - the AI doesn't demand an exact value from every single trade when straight gold is involved and will take things that seem 'close enough'. There's also rounding issues when low amounts of GPT are involved.

Cromagnus said:

My frustration with this mechanic, in my experience, is that you can't ask an AI for its open borders. It has to suggest open borders in the peace treaty or you can't get them.

The problem with this is that I generally consider gpt and luxes to be worth more than cities. So when an AI decides it wants to give me a city, I can't ask for gpt/lux/open borders... I can only ask for gpt/lux.

Click to expand...

I have noticed another similar, annoying issue too: If the AI is getting destroyed, they will give you all of their cities in order to leave them alive. If you get them down to 1 city, though, then their value of "all of my other cities to leave me alone" becomes zero (because they don't have any other cities) and you can't even ask them for gold/lux instead like you could if they had at least one other city.

Oh I didn't see there was another P(WillingtoAccept). I mostly read the original post. I guess it's possible that this is a bug.

But the fact that there are rounding issues involved does not prove this these oddities arise from different mechanics. I thought that AI does not demand exact value every single trade (mostly) because of diplomatic relations. My guess is that at a given time, AI assigns some value to a resource. And his willingness to accept your offer seems to depend on your diplomatic relation with the said AI. Sometimes though, due to rounding issues, AI will be willing to pay higher price for a given resource (for example, 3 gpt for 2 iron but 2 gpt for 1 iron). But this seems different to me than asking for something that he doesn't need, like 4 extra horses that you can remove from the deal.

But knowing that there is another P that "determines how much AI would like to demand from you", you are probably right. It seems weird to calculate this value otherwise.

YourHarry said:

Oh I didn't see there was another P(WillingtoAccept). I mostly read the original post. I guess it's possible that this is a bug.

But the fact that there are rounding issues involved does not prove this these oddities arise from different mechanics. I thought that AI does not demand exact value every single trade (mostly) because of diplomatic relations. My guess is that at a given time, AI assigns some value to a resource. And his willingness to accept your offer seems to depend on your diplomatic relation with the said AI. Sometimes though, due to rounding issues, AI will be willing to pay higher price for a given resource (for example, 3 gpt for 2 iron but 2 gpt for 1 iron). But this seems different to me than asking for something that he doesn't need, like 4 extra horses that you can remove from the deal.

But knowing that there is another P that "determines how much AI would like to demand from you", you are probably right. It seems weird to calculate this value otherwise.

Click to expand...

Luxuries at least have a pretty static value that changes depending on how the AI likes you but is otherwise pretty consistent (Neutral+ is always 7gpt, or 240 gold with DoF; actually kind of odd that you get more with straight gold than you would with gpt since even with DoF you get 7gpt..)

Some other things do fluctuate a little more, though:

ravenmagus said:

Luxuries at least have a pretty static value that changes depending on how the AI likes you but is otherwise pretty consistent (Neutral+ is always 7gpt, or 240 gold with DoF; actually kind of odd that you get more with straight gold than you would with gpt since even with DoF you get 7gpt..)

Some other things do fluctuate a little more, though:

Spoiler :

Click to expand...

If AI does not like you it will not accept a fair deal,so same things cost you more,but the value of items don't change.Luxury always values 240/720.

ravenmagus said:

I have noticed that if the AI is willing to accept peace at all, even if they feel they are in a dominant position and would demand you give up everything you own for peace, they'll just accept a neutral peace treaty anyways.

Click to expand...

a bug

YourHarry said:

A question for the OP. How is the base War score calculated? 0? (EDIT: I meant to say, how is the war score initially calculated? Is it set to 0?)

Never knew that your gold plays such a big role here. Also, is "money yield" just the gold being generated not including the gold per turn you are paying to other civs? For example, if you are generating 100 gold from tiles/religion/policy but you are paying other civs 100 gpt, is the yield 0 (or 100)?

Click to expand...

Yes.Forgot to say.

Yes.You could see your empire's GNP in demographics.