Making and breaking royal marriages
Making and breaking royal marriages is a method by which a player can very cheaply raise relations with another country or countries. "Cheap" here is in terms of treasury money; the method is expensive in stability and diplomats, cheap in money.
In general, making and breaking RMs is a good idea when the following conditions hold:
- your country has a relatively low stability cost (i.e., is small)
- your country has a relatively high level of direct investment into stability, i.e., your monarch has good administration, and/or you've got one or more fine arts academies.
- your country has a good production of diplomats
Doing it is fairly straightforward. For a particular target country, assuming you can make royal marriages, keep breaking them and then remaking them as fast as you get diplomats and/or recover stability. Generally, high relations are not so important relative to technological goals that you should channel your monthly income into stability; if you cannot raise stability a point per year or so without any monthly income, then you probably should not be using this tactic.
Often you will need to pay money to bribe the other country through the "gap" in relations, from -5 to +25, where royal marriages don't work. But other than that, you can get relations all the way up to +200 if you have the time.
One twist is induced by the fact that breaking a royal marriage takes two diplomats, if you have them, not just one. But you can still break a royal marriage with one. Thus, if you can regain stability very fast -- one point in the time it takes you to generate two diplomats -- then it is better to break the royal marriage as soon as you get to 1 diplomat. Otherwise, keeping your reserve diplomats is more important, and you should only break (and then immediately remake) royal marriages when you get to 6 diplomats.