Another part of Kelsen's practical legacy, as he has recorded, was the influence that his writings from the 1930s and early 1940s had upon the extensive and unprecedented prosecution of political leaders and military leaders at the end of WWII at Nuremberg and Tokyo, producing convictions in more than one thousand war crimes cases. For Kelsen, the trials were the culmination of approximately fifteen years of research he had devoted to this topic, which started still in his European years, and which he followed with his celebrated essay, "Will the Judgment In the Nuremberg Trial Constitute a Precedent In International Law?," published in "The International Law Quarterly" in 1947. It was preceded in 1943 by Kelsen's essay, 'Collective and Individual Responsibility in International Law with Particular Regard to Punishment of War Criminals', 31 "California Law Review", p 530, and in 1944 by his essay, "The Rule Against Ex Post Facto and the Prosecution of the Axis War Criminals," which appeared in "The Judge Advocate Journal", Issue 8.