Vassal Infighting

[De Wae]

I'm trying to reverse history as the Byzantine Empire and hold back the onslaught of the Turks. I've taken most of the coastline of the Black Sea and am pushing steadily into Anatolia. My Vassals are perfectly happy with my rule, however they keep attacking their neighbors without my consent! I'm leading about 25k troops in Anatolia while another 6-7k are having a little civil war back home. I've tried to end their plots against eachother but small scale wars still break out, occasionally a vassal will start a border war with a foreign power and I will lose a territory without being able to defend it myself!!! Anyone else having this problem, any tips are appreciated! =)

[Taiwan Number One]

To prevent your vassals from fighting each ohter you'll need medium crown authority, and to stop them from attacking ohter countries you'll need absolute crown authority. Also, you shouldn't be losing land if your vassal loses an offensive war. All that happens is they have to pay for the war and suffer a prestige hit.

[Red Shift]

Also, the pool of troops you draw levies from is different from the pool your vassal does - yours are ring-fenced.
Raising CA will stop your vassals fighting wars via CB, but you will still get hostilities from plots and factions.

[markdb92]

having church vassels will stop alliances from forming reducing de jure wars on even on meduim