World War, 1939-1945 458 History 345 Aerial operations 155 Campaigns 138 Naval operations 124 Aerial operations, American 84 Operations research 80 Armed Forces 72 Aerial operations, British 67 Biography 67 Operating systems (Computers) 67 Naval operations, American 53 Production management 51 Thesis 49 Submarine 48 World War, 1914-1918 48 World war, 1939-1945 47 Management 43 Dissertations, Academic 39 Airplanes, Military 36 Commando operations 34 Personal narratives, American 33 United States 33 Peacekeeping forces 31 Special operations (Military science) 31 Naval operations, British 30 Operational readiness 30 Special forces (Military science) 30 World War 30 Military intelligence 27