This article examines the concept of motherhood and peace in the British women’s movement during the Great War. It does so by focusing on the Women’s International League (WIL) — the British section of the Women’s International League for Peace and Freedom (WILPF). Drawing on the WIL papers, the article shows how a section of the movement continued to lobby for female representation during the war alongside its calls for peace. WIL referred to the social and cultural experiences of motherhood, which allowed it to challenge the discourse on gender and to build bridges between women of former enemy nations. This case study examines how maternalist rhetoric influenced feminism and sheds light on how British women attempted to enter the political sphere by linking women’s maternal experience to their demands for citizenship. In April 1915, approximately 1200 women from twelve nations gathered at The Hague, united in the belief that ‘the women of the world must come to that world’s aid. Emmeline Pethick Lawrence, a former suffragette who turned her attention to the cause of peace upon the outbreak of war, argued that the Hague Congress ‘opened a new chapter in the history of the world-wide women’s movement’. A ‘significant minority’ of British suffragists supported the aims of the anti-war Congress and formed the British Committee of the International Women’s Congress in February 1915 to coordinate their efforts to travel to The Hague. Approximately 180 British women from suffrage, social reform and labour backgrounds responded to the invitation from Dutch feminists, but only three — Emmeline Pethick Lawrence, Kathleen Courtney and Chrystal Macmillan — avoided the wartime travel restrictions and reached the event, held from 28 April to 1 May 1915. On their return to London, they co-founded the Women’s International League (WIL), the British national section of what would become known as the Women’s International League for Peace and Freedom (WILPF). By May 1919 British WIL had 4000 members in fifty local branches. The organisation was largely made up of suffragists and combined radical feminist claims to citizenship with calls for peace and international law. This study of British WIL will shed fresh light on the historical debate surrounding British feminism during the First World War. It examines demands for women’s citizenship and peace during the Great War and in its immediate aftermath. The view that the war was a ‘watershed’ has been quite common, reflected in the argument that the conflict heralded dramatic improvements in the lives of women. More recently, however, this perspective has been increasingly questioned. Susan Kingsley Kent claims that the women’s movement lost its radical edge during the Great War as it seemingly accepted traditional notions of difference between the sexes and reaffirmed the notion of separate spheres, yet she overlooks the prevailing influence of maternalism on feminism before 1914. The relationship between maternalism and feminism has a complex history, which this article will highlight. Women’s activism was both aided and constrained by gendered assumptions about women’s roles. For example, ‘caring’ work and philanthropic efforts permitted some middle-class women access to the public sphere, yet romanticised versions of motherhood placed burdens on working women. Furthermore, women’s international humanitarian relief work could contribute to ideas about empire-building whilst upholding maternal ideals. The latter aspect has recently been illustrated by Emily Baughan’s research on the Save the Children Fund, which was co-founded in 1919 by WIL member Dorothy Jebb Buxton and her sister Eglantyne Jebb. Although WIL was not a relief association, such work influenced the feminism and pacifism of those members who undertook humanitarian efforts before, during and after the Great War. WIL’s roots were entangled with the suffrage campaign, which had argued for equality on the dual grounds that men and women shared a common humanity and that recognition of women’s roles would balance society. A leading group of suffragists resigned from the Executive Committee of the National Union of Women’s Suffrage Societies (NUWSS) during the war, considering their support for peace to continue ‘the principle for which our long fight has been waged’, based on the ‘essential duty of women to uphold the ideal of moral force in human affairs’. These suffragists were involved in the foundation of WIL in 1915. The example of WIL thus illustrates how a prominent section of the British women’s movement remained active during and beyond the Great War. As the article will show, feminists asserted women’s ‘moral force’ — often linked to maternal roles — as an integral part of their ideology and methodology in the campaign for women’s rights and peace, which represents continuity with the maternalist rhetoric of the pre-war women’s movement. WIL stressed the impact of war on women, whilst underlining that feminism was unequivocally opposed to militarism. Furthermore, this article will reveal how feminists of WIL used their understanding of war to demand female citizenship. The discourse of motherhood allowed WIL to operate in the realm of international politics — a traditionally male domain — to demonstrate that women had a valuable contribution to make to the public sphere. Finally, the article will consider the association’s humanitarian and political campaign against the Allied blockade in 1919, demonstrating that maternal rhetoric could unite women from former enemy nations and that women had much to offer to international relations.