random army to army attack from neutral faction with +40 opinion (vassal of my brother)

[Headtaker]

Yeah so i was just moving my army and suddenly my brother's vassal which is not my direct ally but still has high opinion of me attacks my army,
the attacking vassal had a high opinion too,

Is this a bug or something happening which I'm not acknowledged of?

[brownacs]

I could be totally wrong here but I was fairly sure that you can't attack a neutral army. So if I'm the Emperor of the HRE, the King of France is sending some troops through my land and I raise my armies and meet them, they won't fight; they'll just wave hello at each other and continue on their way.

[Slimane]

If you're attacking someone and they have vassals, if those vassals raise their troops they'll be hostile to you. Or if both you and another character declare war on the same enemy, you'll be hostile to each other during the war.

Indirect enemies like that have orange army color instead of red, so try to avoid those armies if possible.

[Headtaker]

Originally posted by Science Denier:

If you're attacking someone and they have vassals, if those vassals raise their troops they'll be hostile to you. Or if both you and another character declare war on the same enemy, you'll be hostile to each other during the war.

Indirect enemies like that have orange army color instead of red, so try to avoid those armies if possible.

We worth both nordic same culture/religion and attacker's leige was my brother so it's still possible? does it disregard the reputation of the attacker?

[Chip56]

The whole concept of "enemy of my enemy is my enemy" is flawed in my opinion and leads to some rather stupid situations.
My personal "favourite":
My vasal, who is actually my wife declares war on an enemy empire to grab a kingdom.
Since she is my vasal i cant join. Okay, fine. She is about as strong as the enemy so she has good chances to win.
Another ally declares war on that same empire for a duchy that is not part of the kingdom my wife wants to grab. This ally can call me into the war and does so.

Result: I am now hostile to the troops of my wife...
While i beat the real enemy armies silly, avoiding my wife and ally the do the following:
My ally and my wife keep conquering the counties the other one just conquered while avoiding an active fight with each other. So both wars are sitting at 80-90% and no one wins because they keep grabing a part of the others war goal, thus avoiding that passivly increasing the warscore. And since they keep capturing each others conquests at about the same speed the total conquered counties does not change.

And i cant further my plans to develop my empire since many of my decisions are locked because of the war.

I really wish the game would check one thing:
"are the war goals of the other wars and mine compatible?"
If yes: count them as ally
If no: count them as enemy.

That would solve so many issues and be far more logical:
A and B want the duchies 1 and 2?: Perfect, lets beat the enemy up together.
A and B want the same duchy 1? "Thats MY stuff. Prepare to die!"

instead of:
A and B want the duchies 1 and 2?: Lets run around and fight each other while our enemy is laughing, winning both wars because neither of us manages to get the full war target.