World War, 1914-1918 21 Guerre mondiale, 1914-1918 17 HISTORY 13 Western 9 Diplomatic relations 5 Foreign relations 5 Relations extérieures 4 Soldiers 4 Weltkrieg 4 Campagnes et batailles 3 Campaigns 3 Diplomatic history 3 Histoire diplomatique 3 Military 3 Military campaigns 3 Military operations, Aerial 3 Aerial operations 2 American 2 General 2 Guerre mondiale (1914-1918) 2 History 2 LITERARY COLLECTIONS 2 Opérations aériennes 2 Prisoners and prisons, German 2 Prisonniers de guerre 2 World War I. 2 psychology 2 Aerial operations, American 1 Aerial operations, British 1 Aeronautics 1