Through diplomacy, realms can declare war on each other.
War can be unilateral or mutual. A unilateral war is when one realm declared war on another but the other realm does not declare war back. All wars last for a minimum of 72 ticks, and once cancelled, realms cannot redeclare on their previous target for 24 ticks.
War can be declared starting on day 6 of the round.
In a mutual war, the bonuses are +10% OP and +20% land gains and prestige and these bonuses become active a further 24 ticks after mutual war is declared.
By declaring war, dominions in both realms can perform the war-only black-ops. This takes place immediately upon declaring war and is not delayed by 24 hours, unlike the OP and land gain bonuses.
In a one way war, successful war-only black ops have a 25% chance to award +1 prestige.
In a mutual war, successful war-only black ops have a 25% chance to give +2 prestige gain, and a 25% chance to give -1 prestige for failed ops.
All black ops are available to be used starting on day 8 of the round.