Over the last twenty-thirty years there has been an increase in conflicts in certain parts of Africa where sexual violence, largely against women and girls, has been widely used as a war tactic to terrorise civilians. Defining wartime experiences and violent encounters is a complex issue. ‘Sexual/conjugal slavery’, ‘forced marriage’ and ‘coercive relations’ are some of the terms that have evolved across international legal, academic and development fields to describe relationships between men, women and children and the harms committed in conflict. In this paper, I explore ‘outsider’ perspectives that inform modern discourses on gender-based violence in Africa. In addition to examining the gender relations of Congolese as understood by Belgian colonialists and missionaries, I trace evolving patterns of early international activism and interventions associated with slavery, marriage and violence. I inquire into the workings of international policy and activism during the colonial period (1908-1960) and the networks and agendas of European non-governmental groups. This approach enables a clear picture of the power structures that undermined women’s positions in the Congo, demarcating “acceptable” forms of femininity from the unacceptable. It also provides historical context to some of the ongoing tensions within contemporary legal, feminist and development discourses focusing on ideas around forced marriage, consent and ‘gender violence’. My work seeks to make sense of women’s conditions and treatment under Belgian colonial control, as well as how marriage, gender and slavery have been framed and used by activist groups to inform interventions over time.