This is one of the few overtly political works written by the key figure in French Sociology. His answer to the question is in the case of the First World War, Germany: hey did so, in part .through a manipulation of Austria. He makes a plausible case of the immediate events precipitating the war but he argument is less persuasive if there is a widening of the reference point to the overall configuration of international relations both at that time - with colonialism rampant, with Spain,England and France, well esconced and Germany and the U.S. and Tsarist Russia joining the race. Introducing history makes easy attribution of responsibilty even harder - while Prussia/Germany invaded France in 1870, one must never forget Napoleon.