War and Peace

Wars
Noble houses cannot declare war on a whim. To declare war, a noble house needs a cassus belli. Cassus bellis are obtained by: To declare war, an emissary must issue the declaration at the other house's estate.
 * Another house’s character rejects an accusation of injustice.
 * A Trial by Combat results in the death of the house's character.
 * An Emperor or Pontiff rules against the other's house in a Trial by Court or Trial by Church as appropriate.
 * Another house attempts to capture one of your starships.
 * Another house attempts to capture one of your vassal’s starships.
 * Another house attempts to capture one of your allies’ starships.
 * Another house commits an act of piracy whilst the law of property is in effect.
 * Another house rejects an Imperial or Church order.
 * Another house assassinates one of your characters and is discovered.
 * Another house sabotages one of your estates and is discovered.
 * Another house spies upon one of your estates and is discovered.
 * Another house imprisons one of your characters at their estate unlawfully (ie. not because the estate was captured or they were caught performing espionage)
 * Another house breaks a truce with any other house

Additionally, if a vassal or liege breaks an oath of allegiance both houses are immediate put on a state of war.

Wars are fought until either a truce or peace is agreed.

Truce
A truce is a temporary cessation of hostilities. The house that breaks the truce (by trying to capture the other house's starships) loses 25% of its honour. Additionally, all houses gain a cassus belli on a truce breaker.

Truces last for one year and then the houses default to a state of war again unless a peace treaty is signed.

Treaties
Truce and peace treaties may have any number of attached land, estates, noble titles, sovereigns or an oath of allegiance that go with from the side offering the truce / peace to the side who accepts it.

All cassus bellis between the two houses are removed once peace is agreed.