Who is Clausewitz from Strategy and what is their importance?

Clausewitz is a German general who figures prominently for his military leadership during one or two chapters. However, the longer term effects of one his "sideline activities", that of having written about and having pondered upon military strategy, turned out to be of great importance even though his widow somehow managed to get his work published even though he had not and may not have even finished it because he died before completion. His influence develops later in the book as an effect of literacy among the more modern military experts and the publication of his military book On War. According to the author, the bad news is that the successful popularization of his works might have caused more bad than good.