Two other suggestion threads have touched on loyalty questions, which are scheduled to be part of a big Society and Politics arc. It's a complex idea, having each person be influenced by multiple group memberships (race, civ, religion, etc.), plus family ties and other individual relationships. And players will want some way to engage with and influence the system.
The oath is the historical answer to loyalty questions. It was the backbone of feudalism. To become a noble or knight,
you had to swear obedience to your lord.
You had to come and fight for him when summoned. In making the oath, you were essentially identifying which group loyalty you considered superior to all the others.
This was a very common idea until quite recently. You had to take an oath to become a monk or nun. The
plot of Pirates of Penzance, which debuted in 1879, is about the protagonist's duties under a contract of apprenticeship. I'm no expert on medieval history, but I bet that some digging would turn up many more oaths that were key to social and political stability.
A forced religious conversion or denunciation is essentially the same idea. The government is unsure of its citizens' loyalty, so it starts demanding public oaths and demonstrations of loyalty to the regime. For example,
Jews faced this in Iberia under Ferdinand and Isabel, and
Christians faced it in Japan under the Tokugawa Shogunate.
Some of the key concepts for implementing this idea:
1.
Different types of oaths. On one end you have an oath of absolute obedience, such as a knight or monk might take. On the other end you have a general oath to follow the law, adhere to the king's religion, and not to aid the king's enemies. Simply by entering the king's land, you might be implicitly bound by such an oath.
2.
Multiple oaths. You can make more than one oath, while specifying which takes precedence. A monk would swear obedience to the abbot, but his oath is subordinate to his pre-existing duty to follow the king's laws. In English history there are often questions of whether a man's duties to the king are subordinate to his duties to God. In the US Civil War there are many stories of brother fighting brother, meaning that there was tension between family loyalty and political loyalty. In practical game terms, each dwarf might have a list of relationships ranked by importance. Urist might have family first, then the king, then his god. While Dastot, being a zealot, puts his god first, then his family, and then the king. Fikot might be so fanatically loyal to the king that he would kill his own family if ordered to do so.
3.
Individual vs Group Oaths. From what I know, early medieval oaths were almost always between individuals. This was part of why the death of the king was such a big deal. Veteran warriors loyal to the old king
might not follow his successor. I think it was a later medieval and early enlightenment idea to swear allegiance to "the kingdom" or "the religion", which greatly improved Europe's political stability. Maybe the dwarven scholars could research that as an advanced law topic. But individual oaths would create more drama and fun.
4.
Oathbreaking is Serious. An oath is a public act. Everyone knows that you've done it. So breaking an oath is also public knowledge, and it's unlikely that anyone will accept an oath from an oathbreaker. The moral stain will even follow you
into the afterlife. An oathbreaker might find refuge with bandits and other disreputable types, but those groups will always be politically unstable because they can't trust the promises that they make to each other.
5.
Requiring Oaths. People who take the oath or belong to the special group get preferential treatment, while others are excluded. This creates stability at the cost of trade and outside contact. For example, Islamic countries imposed a
special tax on non-Muslims. The Tokugawa Shogunate
severely limited trade and foreign contact with Japan for over 200 years.
In game terms, the player should be able to set exclusions based on group membership. Maybe a dwarf can't become a soldier unless he has sworn personal obedience to the duke, or unless he follows a particular religion. Maybe nobody is allowed to visit your fort or trade with it if they follow a particular religion, or if they have contact with your enemies. You could even create castes within the fort: The nice bedrooms and the special dining room is reserved for the praetorian or the true believers, while the commoners or heretics get less. And necromancy should be a particularly divisive issue.
This would give players latitude in creating the type of dwarven society that they want. You could have a fort of racist religious fanatics, or you could a wide-open that accepts everyone including thieves, murders, necromancers, vampires, and animated rotting corpses.
6.
Oaths Don't Last Forever. Either side of the oath contract can publicly
cancel it without penalty, though not in the heat of battle. This would be particularly important in adventure mode, where a player might want to work his way in one civ, and then walk away and start over somewhere else. And all personal oaths to the local lord are cancelled when he dies.