I see a trend of "great leaders" in the responses -- Great leadership cannot be taught separately.
The essentials of leadership can be taught. It is upto the learnee to take those lessons and then transcend to 'great' leadership.
And then, again, leadership principles can only be conveyed. It is upto the learnee to absorb those lessons. As the saying goes, one can only lead the horse to the water.
Leadership principles can be conveyed to anyone - and everyone has the potential to absorb them. Some of them can exploit them further to become great leaders. Saving Changes...