Context is the King. The military style of Leadership is appropriate in one context and wholly inappropriate in another. The same is true for "Heroic", "Guru" and so on. As the needs change, leaders will change. One of the fundamental functions of a leader is to lead change as Change is the only thing constant in life. Change is inevitable and essential to the any organization. Leaders need to be flexible in changing his style based on the environment/context. However, change can be destructive if it is not managed correctly. "Change for change sake" is a bad for everyone.
The famous Financial markets quote 'Past Performance is No Guarantee of Future Results' holds good even for Leadership as Context may change. So the USP of a Leader is ADAPTABILITY.
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I found the below discussion in “LinkedIn Leadership Think Tank Group” particularly interesting.
Major differences between Leadership & Management -
What's Your Favorite Book On Leadership - http://www.linkedin.com/groupAnswers?viewQuestionAndAnswers=&discussionID=9450031&gid=1426