 The development of the book itself, though, was greatly hindered by the war.In June 1940, fleeing the advancing Nazis, de Lubac left Lyon with a bag which included the notebook for "Surnaturel", on which he worked for several days.De Lubac stated in later years that the book had taken sufficient shape by 1941 to be ready for review; the "nihil obstat" was granted in February 1942.