World War, 1939-1945 Campaigns 357 History 353 Biography 122 Aerial operations 69 Naval operations 65 Secret service 46 Regimental histories 43 Aerial operations, British 41 Personal narratives, British 40 Tank warfare 39 Personal narratives, American 38 Germany 36 History, Military 33 Foreign relations 29 Personal narratives 29 Submarine 29 Aerial operations, American 28 Equipment and supplies 27 Naval operations, American 27 Causes 25 Military intelligence 24 World War, 1914-1918 24 Great Britain 23 Soldiers 22 United States 22 Diplomatic history 21 Naval operations, British 21 Prisoners of war 21 World war, 1939-1945 20