just noticed that my Vassal Artois (northern france, channel border, 2PM) just got sneakily annexed by france. I got no notification, no war, or anything.
Suddently everyone in Artois decided to rather be french and switched colors, without anybody even bothering to send me (or my 60k + other, more loyal vassals, Army) even a letter of goodbye.
What happened? And how do i prevent my vassals being sneakily eaten by foreign powers?