Western Roman Empire vs Eastern Roman Empire

[Jansenfinn]

I am playing Western Roman Empire Campaign and Aquincum is already attacked by the vandals but a couple of turns later i helped the ERE to defend Sirmium against the Goths.
We won but after a couple of turns again the ERE comes with a army and siege Aquincum wtf does anyone know why this happends???

[Border Patrol]

You're playing on very hard. It'll happen every time.

[Jansenfinn]

Ok but why the ERE and the WRE are allies for life

[sickpeople]

Its just the R:TW AI.
They want to win - same as you. And they dont really care if you are allied with them, if you have a shared border, they will 100% attack sometime.