This chapter examines the leading, albeit frequently dismissed, twentieth-century professional woman scholar and public intellectual, Jane Ellen Harrison, and her ardent pacifism in response to the First World War, as it puts her in conversation, through her correspondence, commentary, and anti-war, pacifist polemic, ‘Epilogue on the War: Peace with Patriotism’ (1915a), with leading pacifists and anti-war activists such as Bertrand Russell, Goldsworthy Lowes Dickinson, Clive Bell, and Gilbert Murray. Her essay ‘War and the Reaction’, which became ‘Epilogue on the War: Peace with Patriotism’ and was a model and important source for Virginia Woolf’s more well-known pacifist essay, Three Guineas, and Harrison’s other essays on war and humanism, ‘Heresy and Humanity’ and ‘Unanism and Conversion’, each collected in Alpha and Omega (1915b and d), add dimension to a discourse on peace, peace-making, and peace-building that has recently sought to historically construct both aesthetic and active resistance to the war, as well as to act as a counter to the myth of war experience (see Jonathan Atkin’s A War of Individuals: Bloomsbury Attitudes to the Great War (2002); Jay Winter’s Dreams of Peace and Freedom: Utopian Moments in the 20th Century (2006); and Grace Brockington’s Above the Battlefield: Modernism and the Peace Movement in Britain, 1900–1918 (2010)). Here, I explore Harrison’s engagement with and support of the No Conscription Fellowship and the Union of Democratic Control, led by ‘Goldie’ Dickinson, which she backed at great professional risk, incurring the public wrath of her male, pro-war colleagues at Cambridge; her vehement disagreement with her beloved and respected colleague, Gilbert Murray, one of the early crafters of the League of Nations and her close friend, when, in writing to him, she disputed his assumption that ‘War has its good side’; and her public support, again, at great professional risk, of Bertrand Russell. Harrison was read and respected by, and internationally well known to, her contemporaries as a pacifist and a radical, Cambridge intellectual, but her work as a pacifist remains underrepresented. This chapter seeks to act as a corrective, to fill a gap in a critical history in need of acknowledging and investigating her important contributions and efforts to prevent the war.