 Overall, the selection of the diaries and subsequent development work took four years.The series uses cinematic and photographic archive material from a total of 71 archives in 21 countries.Most material came from British Pathé (United Kingdom), Gaumont Pathé (France), Krasnogorsk (Russia), Bundesfilmarchiv (Germany), Österreichisches Filmmuseum, the National Archives and Records Administration (USA) and the Imperial War Museum.