Who is Paul Ree from On the Genealogy of Morals and what is their importance?

Paul Ree was one of Friedrich Nietzsche's closest friends. Four years younger than Nietzsche, he served as a soldier in the Franco-Prussian War. Ree is four years younger than Nietzsche and a doctoral student in philosophy. Ree is the author of the "Origin of Moral Feelings", which was published in 1877.