'Great man theory' was initialized in the 19th century as a leadership theory mostly by Thomas Carlyle. The theory postulated that great men and heroes had so much influence that the course of history, movements and leadership could be traced back to these individuals and their leadership characteristics directly influencing the history of man. Carlyle suggested that their characteristics whether they be personal, political or otherwise gave them a platform to lead from. This platform gave leaders decisive and immediate power to make a mark on the history of humanity and thereby leading in a way that defined them as historical figures.
Herbert Spencer came up with a counter argument around 20 years later which has been the normative perspective up until today's world. He countered great man theory by stating that these great men would not be the decision makers and influencer's if it weren't for the social construct in which they lived. This would of course take the initiative power away from the individual man and show that the man had no power except that which was given to them by the way in which the social structure gave their backing to his development and position.
Ultimately Spencer believed that the society had the leadership power and the society formed the individual to fulfill a role but did not give the 'man' ultimate power and authority to be the history maker.
Although mostly disproved as a possible applicable leadership theory, there are definitions and techniques that we can learn from this. There is strong history behind this short movement but with the sociological thought behind it reveals even more.
If you'd like to see other leadership theories like great man theory then you can see our library of contemporary theories which are more modern.