CK2 wiki said:The target for the GHW must meet the following criteria:
- Target is infidel, or heretic vs parent religion, or pagan vs any
- Target is not a revolt
- Target controls at least 6 counties in the selected de jure kingdom, and also actually possesses the target kingdom title
In my opinion, the "actually possesses the target kingdom title" part is way too restrictive, as it ensures, for instance, no Jihads against Byzantium, as AI emperors don't create kingdoms, and gives the player the ability to dodge GHWs by avoiding creating certain titles. This single condition prompted me to learn to mod the game to change it into something more sensible, but I have no idea where to find it. There doesn't seem to be anything similar either in 00_cb_types.txt or in 00_religions.txt, and the event notifying about the start of a GHW (which is probably purely cosmetic anyway) isn't in crusade_events.txt.