Defecting to Crusades and Jihads

[The Blind King of Bohemia]

Is there anyway you can stop a particular unit from joining a Crusade or Jihad? Does leaving his religion blank help at all?

[Eastside Character]

Only the units of the infidel will never join a Crusade/Jihad army. So the answer is no. Theoretically it is zeal what should control whether and how many men in a province crossed by a Crusade/Jihad will join it, but still it's always a kind of a lottery. The only thing that changes is the probability.

Regards
EC