John Alfred Terraine (15 January 1921 – 28 December 2003) was an English military historian, and a TV screenwriter. He is best known as the lead screenwriter for the landmark 1960s BBC-TV documentary The Great War, about the First World War, and for his defence of British General Douglas Haig – who commanded the British Expeditionary Force on the Western Front from late 1915 until the end of the war – against charges that he was "The Butcher of the Somme".