A declaration of war is a diplomatic action which creates a state of war between two countries.
Abbreviation and Verb Form
"Declaration of war" is rather long, so it is universally abbreviated "DoW" by players. "DoW" is also used as a verb. "DoWed" thus means "declared war".
Preconditions for War
Certain conditions will disallow a country from declaring war. Two conditions will disallow declarations against any other country:
In addition, a country is not allowed to declare war on particular countries which it has certain diplomatic relationships with:
- DoWs are disallowed between members of the same military alliance.
- DoWs are disallowed between members of the same war coalition.
- A country which has received military access from a second country cannot DoW it.
Note that in all five cases above, it is still possible to get in a war with the other country; you just cannot declare war on it. Generally it is not a good thing to be at war with members of a war coalition you're in. But it can be extremely useful to have military access with enemies.
Effects of a Declaration of War
When one country declares war on another, a new war is created. One diplomat is expended, and diplomatic relations between the two countries suffer a drop of -100 points. The country receiving the DoW gets a bonus of +1 point of stability, if its stability is currently below 0.
Both countries have the option of asking their military allies to join their war coalition, but only if they do so at the beginning of the war. The initiating country's war coalition are the aggressors in the war, while the target country's coalition are the defenders.
There may be temporary casus belli created against the country declaring war. Any country which has a warning against the country declaring the war gets a 1 year CB on it. Any country which guaranteed the country that was DoWed also gets a 1 year CB on the country declaring the war.
Sending a declaration of war may incur stability and badboy costs upon the initiating country.
Stability Costs of DoWs
Here is a listing of the stability costs of a declaration of war. Note that these apply only to the country sending the DoW:
- -5 stability: Breaking a truce.
- -2 stability: No casus belli
- -1 stability: Same state religion. This stabhit applies only before the Edict of Tolerance, and never applies to pagans.
- -1 stability: If relations are +100 to +149
- -2 stability: If relations are +150 to +200
Stability Costs of Joining Wars
In addition, some stability costs may be incurred incidentally as a part of entering the state of war. These costs will be imposed on any country entering a war, no matter if it sent the declaration or war or whether it entered the war by other means (alliance call, joining a war when joining an alliance). Here are the costs associated with entering any war:
- -1 stability: Breaking a royal marriage.
- -3 stability: Breaking a vassalization.
Badboy Costs of DoWs
There is no badboy cost for European countries declaring war on pagans. Otherwise, the badboy cost is one of the following:
- +1 BB: DoW with a casus belli
- +2 BB: DoW without a casus belli, with relations +100 to +200
- +4 BB: DoW without a casus belli, with relations -200 to +99
Yes, the badboy hit is worse for lower relations.