Warfare

Version

This article has been verified for the current PC version (3.10) of the game.

War

**Warfare**

Space warfare

Land warfare

As long as there is at least one empire present that is not  Fanatic Pacifist, war is an almost inevitable aspect in any game and can be anything from a small border skirmish to a massive interstellar war of conquest. Wars are how mid-game and end-game borders are usually drawn.

When an AI empire is about to declare war it will first shift fleets towards the border of the target. Targeted empires that have any military intel on the aggressor will receive a warning, with higher military intel levels providing a more accurate estimate on when war will be declared.

## Casus belli and wargoals

In order for an empire to start a war, it needs a  Casus Belli – a reason to declare war. Each casus belli grants access to at least one type of wargoal, which represents the purpose of the war. Once a war is declared, the attacked empire has a year to choose its wargoals.

Status quo effects do not include the defender's capital. In case of status quo the defender will retain its capital system regardless of occupation.

### Subjugation wargoals

Subjugation wargoals seek to end the independence of the targeted empire. If it has any subjects, the effects will apply to them as well. And if the loser is part of a Federation, it will leave it. Subjugation wargoals cannot be used if all systems of the targeted empire are already claimed.

### Paired wargoals

The following wargoals are paired together. If an empire starts a war with either of the paired wargoals the defender will automatically use the other wargoal and cannot pick another one. In case of the Allegiance War casus belli all empires which swore secret fealty to the attacker will join the attacker's side.

Paired wargoals with **−1000** surrender acceptance lead to a Total War. In Total Wars, all occupied systems automatically change ownership. Their new owner will be the participant with the highest claim count on it or the occupier if none of their allies claim the system.

## Claims

While casus belli and wargoals represent the purpose of a war, **claims** represent territorial ambitions — the systems which will be controlled by the victor. Which systems can be claimed depends on an empire's  War Philosophy policy, with the Unrestricted Warfare philosophy allowing for the claiming of any system not owned by a fellow  Federation member. It is possible to claim the same system multiple times to gain a stronger claim on it, which can outbid the competing claims of allies when going to war together. If multiple empires have the same number of claims on a system the oldest claim is considered the strongest. In general claims are expensive in the early game and become less so later on to allow for more decisive wars to be fought. Claims cannot be rescinded while at war.

Claims have a base cost of 50  influence, modified by the following:

* **+25** per hyperlane distance from owned territory
* **+25** if the system has an upgraded  Starbase (i.e. not just an Outpost)
* **+25** if the system is colonized
* All costs are increased by **+100%** during an offensive war
* All costs are reduced by **−20%** if the claimed system belongs to a Rival

If the modifier reaches a total of **–100%**, claims then cost 0  influence.

Defenders can freely claim systems owned by their attackers in a defensive war regardless of their War Philosophy policy. Any system lost by any side during a conquest war or total war will give the former owner 10 claims on it.

Winning war with any non-conquest wargoals will always enforce all claims made by the victorious empires before any other effects, regardless of whether these systems were occupied. For example, an empire winning a war with the subjugation wargoal will annex all claimed systems from the loser before making a  Vassal of the loser's remaining systems.

## Federation warfare

The Federation is the more serious counterpart of the Defensive pact and the inviting attackers mechanic. While it does offer a unique amount of defensive cooperation, builds trust and allows military cooperation using the federation fleet, establishing a conquest strategy can be made very difficult because of the need for consent of the members to declare war, and each member's expectation of a fair share of spoils from each war. The empire that wishes to declare war can ask the other federation members for their war goals by using the "Suggest Demands" button. However, AI empires will be very hesitant to declare war on empires that are much stronger than them or have very powerful allies. In that case, the "Suggest Demands" button will not give any results.

One exception to this are wars of liberation or to a lesser extent vassalization: usually AI will agree to a liberation war even if all the war goals are assigned to the player. The resulting splinter empire could then be vassalized and later integrated by the player.

In case a federation member is attacked, all allies automatically join the war as defenders without need for a further declaration of war. In this case, the member being attacked has a free hand in choosing federation war goals, which might be all in its own favor.

## Ending wars

Wars can end in two ways: With the surrender of either side or with a negotiated Status Quo peace.

**Surrender** means that the victor's wargoal is enforced; any claims the winning side has on the losing side are automatically ceded regardless of occupation status and the defeated empire is forced to keep borders open towards the attacker for 10 years. All wars except those of independence have a negative surrender acceptance, which are countered by factors such as relative navy strength (up to +50), war exhaustion (up to +100) and occupation percentage (up to +100). If an empire and all of its allies (if any) has lost control of all of its systems and/or planets during the war, then a surrender will occur automatically.

**Status Quo** means that the war has reached a point where neither side is able to score a decisive victory against the other or all wargoals have been achieved decisively before any major battles took place, and both sides agree to cease hostilities and settle for whatever gains or losses they have acquired/suffered. Under a Status Quo peace, all **fully** occupied systems claimed by a belligerent empire are ceded to the belligerent with the strongest claim. In the case of a tie, whoever has the oldest claim on the system is considered the stronger claimant. In addition both sides must keep their borders open towards each other for 10 years. Since AI won't surrender to a Total War, they can end only in Status Quo or the destruction of one empire. Status Quo can be enforced by either side as soon as 24 months have passed since the opposing side reached 100% war exhaustion, and if both sides reach 100% war exhaustion, the Status Quo is enforced automatically after 24 months.

### War exhaustion

War Exhaustion goes from 0% to 100%, and measures the total weariness and attrition suffered by all empires on one side in a war. War exhaustion goes up from suffering losses during space and ground warfare, destruction of planets (either from Colossus weapons or  Armageddon Bombardment), and a passive accumulation over time called Attrition. When a side's war exhaustion hits 100% they can be forced into a status quo peace after 24 months. The speed at which war exhaustion accumulates is influenced by factors such as ethics, traditions, technology and the amount of claims being pressed - an empire that is fighting to hold onto a handful of border systems will tire faster in a costly conflict than one whose very independence is being threatened. War exhaustion also means that an empire that is losing a war can still fight to minimize their territorial losses by inflicting high war exhaustion on the enemy.

War exhaustion gain can be lowered by the following factors:

## War names

Wars will always be named after the attacker and the defender, followed by one of the following names depending on the wargoal: