Ming said:
Is there any way to move and defend a castle the turn it is built? i.e. the castle would be completed the turn the troops arrive but not yet completed when one issues the move order.
Edi, IIRC normal build orders resolve after all the battles for a turn are complete, so a simple move order should suffice to defend the castle's province that turn.
In the case of spells and events that pop forts up immediately Edi's answer holds.
I should have checked back earlier as I have just learnt it the hard way (not sending troops thinking it cannot be defended and that I should at least have the new castle protecting my lab and temple) Fortunately I am only playing against the AI. 8-)