Don't start a sentence with "But", and avoid using personal pronouns e.g. he, she and I etc. too often to start a sentence.
The objective of the essay is not clear. "Hero" seems to be the objective because it is clearly defined in the first sentence. However, only "Napolean" is described in the heart of the essay and the concluding paragraph. We all know that there are thousands of heroes in the world's history and Napolean is only one of them. If this essay were meant to describ Napolean as a hero, the 1st sentence has to be altered to include "Napolean".