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 48 ticks, and once cancelled, realms cannot re-declare on their previous target for 48 ticks. Invasion bonuses for war linger for 12h after cancelling.
War can be declared starting on day 4 of the round.
In a mutual war, the bonuses are +10% OP and +20% land gains and these bonuses become active a further 24 ticks after mutual war is declared. Additionally, the following bonuses become active immediately after the mutual war declaration: -20% spy/wizard losses from war operations, +20% infamy gains, -50% resilience gains.
By declaring war, dominions in both realms can perform 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. Black ops will no longer be available after war has been cancelled while invasion bonuses linger for 12h
All black ops are available to be used starting on day 4 of the round.
Wonders in another realm cannot be interacted with until invasion bonuses between those realms are active (24h after declaration). Once war has been cancelled Wonder access is removed, unless the other realm has their own active war bonus.