Olympia: The Age of Gods PBEM (Oct 4 2000)
A moving stack may be attacked from the location in which it began its move until the end of the day the move completes. (Note: a stack may receive a message that it has "arrived" in a location and still be attacked later that same day by a stack in the location where it began travel.) It may not be attacked from its destination until the move completes.
If an attack against a moving stack succeeds, the movement fails and the stack remains in its original location. If the attack fails, the movement completes.