Terrestrial Warfare

Wars begin when a councilor for the executive faction on one of the two rivals selects the War policy against the rival. All war-capable allies of the defending rival (with an army or nuclear weapons) join the war. All war capable allies of the attacker are given the option to join on the attacker's side.

To win a war, an army must occupy the enemy's capital region. At that moment, the war ends, triggering a regime change event. Claimed regions change hands to the occupier and its allies. If any of the invaded nation remains, its control point owners are replaced with those of the victor. Some of the nation's stats change when a new regime is installed, sometimes in unpredictable ways, but the new ruling faction will be able to fund Direct Investment into the nation without paying an influence cost for a period of one year.

Unoccupied regions and surviving enemy armies will contribute to greater unrest following a regime change.

Wars may also end with a white peace, where both sides return to 'status quo ante bellum'.

### Armies

Armies represent multiple modern divisions that are capable of gaining and holding territory in other nations. Control of an army is gained after councilors gain at least partial control of a nation. Most nations don't have armies at the campaign start, but nations with sufficient population can build new ones with enough investment. While powerful, armies are a drag on the nation's economic development and remain subject to the international relations of their home countries, which too can be managed with sufficient control of a nation.

Armies have a headquarters region in their home nation. If located there, they incur a smaller cost to the nation's economic development.

Armies rely on two key values: its parent nation's Miltech level and its strength. The strength value measures how much damage the army has taken. Armies repair themselves when not fighting in a friendly region.

Some armies have a Navy upgrade that allows them to transit across oceans, representing a nation's ability to transport, support and protect the expeditionary forces with naval assets. During wartime, a nation's navies can only cross the water if the nation has naval superiority over its foes. Only the larger or wealthier nations have the capability to build and project power with navies.

### Army Operations

The faction that controls an army can conduct operations with it. They are:

* **Deploy Army** - Move this Army to an adjacent region, including those of allies or wartime enemies. Armies will engage in battle with enemy armies and occupy enemy regions. Naval armies may move between coastal regions worldwide if no belligerent power has naval superiority.
* **Deploy Armies** - Move this and all of your faction's eligible armies from here to an adjacent region.
* **Assault Alien Asset** - Launch an assault on a fixed alien target.
* **Assault Space Facility** - Destroy a fixed space facility in the region.
* **Raze Region** - Launch a general attack on economic and civilian targets in this region. Counts as an atrocity.
* **Airlift Home** - Return this army to its home region during peacetime. Operation will not complete if home nation is at war.

### Army Battles

If at least two enemy armies are in the same region, they will fight. Mechanically, each army takes a shot once a day. Its chance of successfully damaging an enemy army is based on its Miltech level, strength, whether any councillors are lending their command attribute to the army's nation via the Advise mission, and whether it is on defense and the region has the "rugged" flag set.

If an army is in an enemy region and no enemy armies are present, it begins occupying the region, battling the local defense forces (who use the nation's Miltech level) and taking damage from them. Badly damaged armies will attempt to flee to a safe place without you losing anything, but they can also be destroyed entirely when their strength reaches zero.

If a region is fully occupied it ceases fighting, but it can't change hands until the war is concludes. Regional economies and space facilities can take significant damage during fighting, although the rate of damage goes down as Miltech goes up (representing more precise weaponry). Sufficient damage will count as an atrocity by the army's owning faction.

### Naval Superiority

During wartime, a nation must have higher naval score than its enemies to be able to transport troops across the ocean. It will be shown as blockaded if such movement is prohibited.

A nation's naval score is calculated by the number of navies it has attached to armies multiplied by the nations Miltech score.

### Nuclear Warfare

Some nations have a number of nuclear attacks available to them. These represent launching multiple strategic nuclear weapons at a target region. Launching nuclear strikes will devastate the economy of a region and the enemy armies within it, although the damage will be somewhat mitigated if the nation is launching strikes on its own or an ally's territory. Launching factions will be charged with committing one or more atrocities. Detonating a sufficient number of nuclear weapons may also have disastrous global effects.

Completing the nuclear weapons priority can add more nuclear attacks for a nation.

Nations construct nuclear weapons as a deterrent to enemy invasion. Attempting to conquer a nuclear-armed nation will almost certainly lead to nuclear strikes in retaliation.

As of the demo version of the game, It must be noted that the investment cost of producing a nuclear barrage is significantly lower than producing an army, let alone incorporating a navy to said army (for a total of 25 points vs 160); a detonating barrage will always cause lethal damage to an army. Because of this, nuclear confrontations can lead to stalemates in which more nukes are being produced rather than armies to finish the war, with disastrous consequences for Earth. A such, nuclear deterrence makes for a powerful tool even in the hands of the AI.