Siege assisting

[unmerged(48708)]

Im slightly confused here. During a recent campaign on Carthage most of the world decided to join in except my only allies Rome.

At some point Bosperus send in a stack by sea to a province I had a stack marching on. Now I can see the point in first to siege=winner of territory.
But what happened was that Bosp assualted as soon as my stack entered...and didnt win the siege. My stack took no casualties, which at least makes some sense, we arent allied and he shouldnt be allowed to force casualties on me. My stack did however go to 0 morale along with Bosp, and was then wiped out by a 1K militia stack that arrived before months end.

Now is that something I need to be on the lookout for in the future, or just a fluke?

 

[Battlecry]

It happens. When one army is besieging a province and another arrives, an assault frequently ensues, which usually fails because the player is not intending/prepared for an assault. Being wiped out by an arriving 1K unit, however, is uncommon ad extremis.

 

[unmerged(48708)]

Good to know. It was merely a 5k siege stack and Bosp cant have had much Im guessing a 2k stack depleted from the siege.
So I can assume that Ill only ever take the morale loss and dont actually participate in the assualt?