History World War, 1939-1945 Campaigns 141 Aerial operations, British 31 Biography 28 Regimental histories 25 Naval operations 23 Equipment and supplies 21 Germany 21 Aerial operations 17 Armed Forces 15 Secret service 15 Airplanes, Military 13 Great Britain 13 Military intelligence 13 Aerial operations, American 12 Tank warfare 12 United States 12 World War, 1914-1918 12 Siege, 1942 - 11 Underground movements 11 Prisoners of war 10 Japanese occupation 9 Personal narratives, American 9 Pictorial works 9 Diplomatic history 8 Soldiers 8 World war, 1939-1945 8 Campaign 7 Causes 7