I remember when the trades formally announced that Liam Neeson would be starring in Batman Begins... they announced him as Ra's al Ghul. Then, not even a day later, the trades (I think it was Variety or the Hollywood Reporter) corrected themselves and said Neeson was actually playing Ducard, much to the chagrin of fans everywhere.
A former co-worker of mine insists that in Batman Begins
"Ra's al-Ghul" is a title
for the head of the League of Assassins, and that when Bruce kills Watanabe-Ra's and burns down their fortress, the highest ranking person left is Ducard who becomes the new Ra's al-Ghul.
I'm not sold on the theory, but I can accept it as a valid interpretation of the evidence in the film.