Just a thought, this would be a cool mission for spymasters or perhaps marshals.....would be a nice feature to implement.
You could have for example CB to rescue member of your dynasty or ally.
We need other plots than assassinations anyway.A new plot to rescue a prisoner is what we need.
We need other plots than assassinations anyway.
That happened a lot historically. It would work if the engine could dynamically change a CB. For example, if prisoner dies then CB changes to take prisoners of your own.You can't wage war if your close kin is bethrothed or imprisoned by the guy you're trying for attack.
The war would be like this:
King X declares war on king Y to free prince Z.
King Y executes prince Z because he is from an enemy country.
War ends inconclusively (casus belli no longer valid).