Vasall armies hostile to me in foreign war -> intended?

[Veiovis123]

Recently, my daughter, an independent ruler of Minsk, attacked the Queen of Ruthenia in a holy war (my daughter belongs to my custom religion, as does my entire dynasty).

She is helped in this by several of her cousins, which are my vasalls (which are all at + 100 relations).

I used the opportunity to also declare a holy war against ruthenia, but for a duchy far arway from my daughters wargoal. Sadly, this causes my vasall and daughters army to become hostile to me, slamming against my armies, being destroyed. Some of my nephews (that love me!) are even being killed in those fights, as I can't micro enough to avoid them all.

So in short, my co-religionist vasalls are attacking my armies, because I wage a separate holy war with no overlap in goals against their enemy. Is this a bug or intended behavior?

 

[Swamphill]

Yes, for CK3 they went for an inclusive hostility. If A is at war against B in one war and against C in another the armies of B and C are hostile to each other. This is a departure from how it works in eg EU4 where B and C would not be hostile to each other.

 

[Comrade_Boris]

Note, their armies should also be highlighted in a pale red-orange color instead of the usual red hostile army color. This indicates that they are hostile, but not part of your war.

The advantage of this mutual hostility system is that if say your daughter occupied a county that is your wargoal, then you can fight her to occupy it. The disadvantage, as mentioned, is that you can be embroiled in fights that are not yours.

Also worth noting, if you play as a vassal a similar behavior happens when your liege is in a war. The hostile armies are in this half hostile state to you, whether you join the war or not. This is also nice because you can choose to defend your territory without actually declaring war.