共同防御协定

共同防御协定往往是由多个势力组成的联合，旨在遏制某个极具侵略性的目标国家。如果被针对的目标国家进攻其中一个成员，那么共同防御协定的所有成员都将会被视为同盟，共同加入到对抗目标国家的战争当中去。

衡量一个势力会不会加入或建立共同防御协定，取决于目标国家的威胁度：它随着蛮横的扩张而增加，也随着时间的流逝而减少。

在游戏开始的设置中，可以选择禁止共同防御协定的诞生。

威胁度

增长

每个被征服的省份都会使您增加2%到15%的威胁度，这取决于您的疆域大小（？），与宣战借口也有一定的关系。通常而言，以宣称或者法理为借口篡取的土地会带来更低的威胁度。另外，使用外交手段要求其他势力臣服，或者在统治者的情况下继承头衔也会增长威胁度，但往往并不显眼。单一来源最多带来50%的威胁度。

如果您的封臣产生了威胁度，其中一部分会加到您的头上，如此增加的威胁度很明显比不上您亲自动手，因为每个特定的封臣都太小，不会对一个国家构成太大的威胁。

减少

威胁度每月会自动减少0.21%到0.4%，这取决于您的兵力（？）。如果DLC已经启用 修道士与密契者 ，您就可以在内阁界面为外交总管分配一个减少威胁度的工作。

任何离开你国家的土地都可以减少威胁；这包括因继承和征服而失去的土地。然而，当一个封臣通过获得与他们的领主相同（或更高）等级的头衔而独立时，失去的土地不会减少威胁。

Granting independence会根据释放的郡县数量减少威胁。这鼓励你释放外围的附庸，尤其是那些由于法律结构而提供较少徭役的附庸。释放你最远的附庸也可以缩小防御协定，因为靠近你边界的外国领地会减少。

最好是你已经和你计划释放的附庸签订了互不侵犯条约，这样他们就不能加入防御协定；如果被释放的附庸不信仰你的宗教，这一点就更重要了。此外，你还可以请求结盟。

威胁等级

在威胁程度较低的情况下，防御协定的成员按宗教团体组织；请注意，追随某宗教异端的统治者可以和追随主流宗教的统治者一起加入协定。随着威胁的增加，即使是异教徒也会在防御你的时候一起战斗。

Threat	Effect
5%	针对你的防御协定的最低要求
50%	你以外的宗教团体将联合起来
75%	所有的宗教团体将联合起来
95%	甚至你的宗教领袖和骑士团也将加入所有的战争

威胁上限为100%。因此，任何超过100%的威胁都将丢失。

Membership

In my ERE game, I see fellow Christians only joining defensive pacts when I have a CB, and even then not always. On the other hand, Pagans far too distant for holy wars are all in the pact. This isn't fully explained by what I gathered below, from reading defines.lua. What am I missing?

Any realm can join a defensive pact against you if:

• Your threat is at least 5%
• They are smaller
• They are within 300 distance, or 400 distance if another religion group

AI will consider joining against you if:

• You could attack me: Less than 80% troop strength and you have a CB (except "Make tributary" or "Humiliate nomad"?)
• You're too big: Less than 20% your size in provinces
• Pact needs assistance: pact is less than 70% strength, an existing member of their religion/culture/dynasty, and you are not

AI will then compute a score to decide whether to actually join:

 [(1.0 × provinces) + (150 × threat) + (-1.1 × distance)] * cb_multiplier

They will join with a score above 110 and leave with a score below 70.

Strategies

There are many things you can do other than simply waiting for threat to decay.

Go all in

When fighting a war that would take you from 40% threat to 90% threat, declare as many other wars as you can handle at the same time. This is your last chance to attack moderately weak realms until (1) you can take on entire regions at once or (2) your threat decays.

With the Conclave DLC, if your council can vote on war declarations, be sure to have Glory Hounds voting if you wish to pursue this strategy and not cause tyranny and council discontent.

Attack targets who are not in defensive pacts

• Attack new realms the day they are created, before they have a chance to join defensive pacts. Make sure you have a CB ready.
• Pick off vassals who are rebelling against their liege.
• If a realm has not yet joined a defensive pact, avoid gaining a CB on them until you're ready to attack. For example, only invite a claimant at the last minute.
• Invade realms that are stronger than you on paper, increasing your de facto power through alliances or by hiring mercenaries and holy orders.

Blitz small members

Pick off tiny defensive pact members by assaulting their holdings very quickly. If you completely occupy the target realm before the rest of the defensive pact shows up, you have 100% warscore and can declare the war over.

The main problem here is that levies cannot be raised when declaring war. Retinues or mercenaries, on the other hand, can be days away from arriving in the province. These professional armies are expensive, but there are many ways to gain wealth.

Another obstacle is the presence of upgraded castles; castles with fort level 6 and above cannot be assaulted; be sure to check the fort levels of castles before declaring war.

If a realm is slightly too large for a quick retinue assault, you can use a two step plan. First, find an excuse to be hostile to their armies and holdings. Use levies to weaken them as much as possible. Second, declare war on them and finish them off with retinues.

There are several ways to become hostile to a realm without incurring a truce or getting the defensive pact involved:

• Being allied to their enemy:
  • Join an ally in a war where your target is on the other side
  • Join a coreligionist in a holy war
  • Join a rebelling vassal (overthrow_ruler* rebellions only)
• Being at war with their rebelling vassal
• Raiding

Support vassals in their external wars

• Establish strong vassals near your borders, even if you normally prefer to have weak vassals.
• Raid neighbors and destroy their armies, so your vassals are more inclined to declare war.
  • Alternatively, raid your vassals' targets as they fight their wars.
• Assist vassals with cash gifts, defeating their enemies' armies, or (depending on the CB) joining their war

Form non-aggression pacts

• It helps to have a large family.
• Use favors to arrange marriages with infidels. You probably won't be able to buy a favor from a ruler who is in a defensive pact against you, but you might be able to buy a favor from their heir for use later.
• You can even create a non-aggression pact with a betrothal, immediately break the betrothal, and attack. This is considered "gamey".

Use tributaries

• Making a realm your tributary forces them out of a defensive pact without increasing threat. It also increases your effective strength (since you can call tributaries to war) without allowing stronger realms to join the defensive pact.
• Good against empires or any other realm from which you can't take a significant fraction of land in a single war.
• If you do get a good CB against them later, you can release them from tributary status and immediately attack.
• Forcing tributaries to join your wars may weaken your tributaries enough to trigger revolts. You can then declare wars on the revolts freely.
• Use the CB for a tributary type which persists through succession.

Be a vassal

• When you conquer territory, any defensive treaty formed will be against your liege lord, who is perceived as the ultimate owner of this territory, and won't be triggered by future wars you initiate.
• This means that vassal khans can expand with greater impunity than their Khagan.

Modding

Search defines.lua with the following regexp: infamy|threat|coalition|defensive_pact

See also

Other PDS grand strategy games have related mechanics:

• Victoria 2 has Infamy. Internally, it is called BadBoy.
• Europa Universalis IV has a more nuanced version of threat called Aggressive Expansion, a relation modifier that indicates how threatened each nation is by your actions. When Coalitions form in EU4, they can act aggressively to dismantle a threat.