A central thesis is the "main argument the essay is trying to say".
For example, inside the essay on war, your thesis should include the 3 (more or less) claims that you are going to talk about, such as "The art of War", "History of War", "Outcomes of war", in which you would talk about the 3 topics and not only explain but give explanation of this, and give a conclusion of how this affects not only our history, but our world even today. The thesis statement must encompass all that you would talk about.
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