Father Daniel A. Lord page 8 of It's Christ or War stated 2 professors (exiled Russians) in America studied wars on the basis of numbers actually engaged, and numbers engaged in proportion to the world population of the time, number of casualties, numbers of countries involved, disastrous effects. Petirim Alexandrovich Sorokin and Nikolai Nikolaivich Golovine. (made a graph about 1925)
With zero for absolute peace, they found that the century of greatest world peace, with the percentage only 2.7, was the year 1100-1200. The first quarter of our century rises to 13,735.98.
I found this to be quite interesting, even though I can't give you a book, but this one. It is a booklet. It is not in depth of those years that you speak of.