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Thread:Bah-Lamine/@comment-4374396-20111015184804/@comment-3058930-20111016132742
Communication between different countries at that time would of been difficult. Having one Mentor who controlled the entire Order wouldn't of worked. If he was (for example) in England and wished to send Orders to the Assassins in India, it would of taken a while. That's why there were Grand Masters for each Guild.
However, by modern times, when communication was much faster, the Assassin Order had "the Mentor", who controlled the whole Order.